Image reading apparatus for detecting a shadow region formed by end of conveyed document

ABSTRACT

An image processing apparatus includes a transparent member, a white reference member, an imaging device, a conveyance member, a light source, and a processor for detecting a dirt substance from the input image. The light source is provided such that a shadow of a leading end or rear end of the document conveyed on the transparent member is formed on the white reference member at the imaging position. The processor detects a shadow region formed by the leading end or rear end of the conveyed document from the input image and detects a dirt substance from within the detected shadow region.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority ofprior Japanese Patent Application No. 2018-044767, filed on Mar. 12,2018, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to image processing technology.

BACKGROUND

An image reading apparatus, such as a scanner, typically captures animage of a document while conveying the document using an imagingdevice, such as a line sensor, where imaging elements areone-dimensionally arrayed. If a dirt substance, such as paper dust,other fine particles, or glue, adheres to a glass surface of the imagingdevice, noise line extending in a document conveyance direction isgenerated in an image captured a document. Thus, an image readingapparatus and an image processing system having an image readingapparatus need to appropriately detect a dirt substance from an image.

There has been disclosed an image reading apparatus that includes aconveyance device that conveys a document along a conveyance path, a CCDunit that reads a document at the reading position in the conveyancepath, and a control module that controls to read a shadow of a documentbeing conveyed along the conveyance path. This image reading apparatusdetermines a dirt substance at a reading position based on the shadow ofa document read by the CCD unit (refer to Japanese Unexamined PatentPublication (Kokai) No. 2010-74530).

SUMMARY

An image reading apparatus and an image processing system having animage reading apparatus is desired to better detect a dirt substancefrom an image of a document and a periphery of the document.

It is an object to provide an image reading apparatus, an imageprocessing system, and a dirt substance detection method that can betterdetect a dirt substance from an image of a document and a periphery ofthe document.

According to an aspect of the apparatus, there is provided an imagereading apparatus. The image processing apparatus includes a transparentmember, a white reference member provided either above or below thetransparent member, an imaging device for, provided on an opposite sideof the white reference member across the transparent member, generatingan input image of a document and a periphery of the document conveyedbetween the transparent member and the imaging device at an imagingposition, a conveyance member for conveying a document between thetransparent member and the imaging device, a light source for, provideon an opposite side of the white reference member across the transparentmember, irradiating light toward the white reference member, and aprocessor for detecting a dirt substance from the input image. The lightsource is provided such that a shadow of a leading end or rear end ofthe document conveyed on the transparent member is formed on the whitereference member at the imaging position. The processor detects a shadowregion formed by the leading end or rear end of the conveyed documentfrom the input image and detects a dirt substance from within thedetected shadow region.

According to an aspect of the system, an image processing system isprovided. The image processing system includes an image readingapparatus including a transparent member, a white reference memberprovided either above or below the transparent member, an imaging devicefor, provided on an opposite side of the white reference member acrossthe transparent member, generating an input image of a document and aperiphery of the document conveyed between the transparent member andthe imaging device at an imaging position, and a conveyance member forconveying a document between the transparent member and the imagingdevice, and a light source for, provided on an opposite side of thewhite reference member across the transparent member, irradiating lighttoward the white reference member, and an information processingapparatus including a processor for detecting a dirt substance from theinput image. The light source is provided such that a shadow of aleading end or rear end of the document conveyed on the transparentmember is formed on the white reference member at the imaging position.The processor detects a shadow region formed by the leading end or rearend of the conveyed document from the input image and detects a dirtsubstance from within the detected shadow region.

According to an aspect of the method, there is provided a dirt substancedetection method for an image reading apparatus including a transparentmember, a white reference member provided either above or below thetransparent member, an imaging device for, provided on an opposite sideof the white reference member across the transparent member, generatingan input image of a document and a periphery of the document conveyedbetween the transparent member and the imaging device at an imagingposition, a conveyance member for conveying a document between thetransparent member and the imaging device, and a light source for,provided on an opposite side of the white reference member across thetransparent member, irradiating light toward the white reference member,wherein the light source is provided such that a shadow of a leading endor rear end of the document conveyed on the transparent member is formedon the white reference member at the imaging position. The methodincludes detecting a shadow region formed by the leading end or rear endof the conveyed document from the input image, and detecting a dirtsubstance from within the detected shadow region.

The object and advantages of the invention will be realized and attainedby means of the elements and combinations particularly pointed out inthe claims. It is to be understood that both the foregoing generaldescription and the following detailed description are exemplary andexplanatory and are not restrictive of the invention, as claimed.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a configuration view of an example of an image processingsystem according to an embodiment.

FIG. 2 is a view for illustrating a conveyance path inside an imagereading apparatus.

FIG. 3 is a perspective view of a first imaging unit seen from the sideof a document conveyance path.

FIG. 4 is a view for illustrating the imaging unit and a conveyancemechanism of the upstream and downstream sides of the imaging unit.

FIG. 5 is a view for illustrating the arrangement of a first conveyanceroller and a first driven roller.

FIG. 6 is a view for illustrating how a document is conveyed.

FIG. 7 is a view for illustrating the arrangement of a first lightsource and a first imaging sensor.

FIG. 8 is a block diagram depicting schematic components of an imagereading apparatus and an information processing apparatus.

FIG. 9 is a view depicting schematic components of a first storagedevice and a first CPU.

FIG. 10 is a view depicting schematic components of a second storagedevice and a second CPU.

FIG. 11 is a flowchart depicting an example of the operation of theoverall processing of the image reading apparatus.

FIG. 12 is a flowchart depicting an example of the operation of firstprocessing.

FIG. 13 is a schematic view depicting an example of a white referenceimage.

FIG. 14A is a schematic view depicting an example of a reception screen.

FIG. 14B is a schematic view depicting an example of a status displayscreen.

FIG. 14C is a schematic view depicting an example of a status displayscreen.

FIG. 15 is a flowchart depicting an example of the operation ofconfirmation processing.

FIG. 16 is a flowchart depicting an example of the operation ofthreshold setting processing.

FIG. 17 is a flowchart depicting an example of the operation of theoverall processing of an information processing apparatus.

FIG. 18 is a flowchart depicting an example of the operation of secondprocessing.

FIG. 19A is a schematic view depicting an example of a correction image1900.

FIG. 19B is a schematic view for illustrating a plurality of linesegments.

FIG. 20A is a schematic view for illustrating a priority range.

FIG. 20B is a graph for illustrating noise pixels.

FIG. 21 is a flowchart depicting an example of the operation ofcorrection processing.

FIG. 22 is a graph for illustrating a relationship between a noise lineand the background of a document.

FIG. 23A is a graph for illustrating a relationship between a noise lineregion and a content.

FIG. 23B is a graph for illustrating a relationship between a noise lineregion and a content.

FIG. 23C is a graph for illustrating a relationship between a noise lineregion and a content.

FIG. 24 is a schematic view depicting an example of a correction imagein which a noise line region overlaps a character.

FIG. 25 is a view depicting schematic components of an imaging unitaccording to another embodiment.

FIG. 26 is a view depicting schematic components of an imaging unitaccording to still another embodiment.

FIG. 27 is a block diagram depicting schematic components of a firstprocessing circuit according to another embodiment.

FIG. 28 is a block diagram depicting schematic components of a secondprocessing circuit according to still another embodiment.

DESCRIPTION OF EMBODIMENTS

Hereinafter, a document conveying apparatus, a control method, andcomputer program according to an embodiment, will be described withreference to the drawings. However, note that the technical scope of theinvention is not limited to these embodiments and extends to theinventions described in the claims and their equivalents.

FIG. 1 is a configuration view of an example of an image processingsystem 1 according to an embodiment.

The image processing system 1 includes an image reading apparatus 100and an information processing apparatus 200. The image reading apparatus100 is an example of the image processing apparatus, such as an imagescanner. The image reading apparatus 100 may be a photocopier, afacsimile, or a multifunction peripheral (MFP). The informationprocessing apparatus 200 is another example of the image processingapparatus, such as a personal computer, a multifunctional mobileterminal, or a mobile phone. The image reading apparatus 100 and theinformation processing apparatus 200 are mutually connected.

The image reading apparatus 100 includes a lower housing 101, an upperhousing 102, a document tray 103, side guides 104 a, 104 b, adischarging tray 105, a display operation device 106, etc.

The upper housing 102 is arranged at a position for covering the uppersurface of the image reading apparatus 100 and engaged with the lowerhousing 101 by a hinge such that the upper housing 102 can be opened andclosed when a document is jammed or for cleaning the inside of the imagereading apparatus 100, especially, the imaging position of the imagingsensor.

The document tray 103 is engaged with the lower housing 101 androtatable in a direction of arrow A1. When the image reading apparatus100 is not in use, the document tray 103 is arranged at a position forcovering the upper housing 102 and the lower housing 101 and functionsas an exterior cover. Whereas, when the image reading apparatus 100 isin use, the document tray 103 is arranged at a position on whichdocuments can be placed and functions as a document placing tray.

The side guides 104 a and 104 b are provided on the document tray 103movably in a direction A4 perpendicular to a document conveyancedirection A3. The side guides 104 a and 104 b are aligned with the widthof a document placed on the document tray 103 to regulate the widthdirection of the document.

The discharging tray 105 is housed inside the lower housing 101 suchthat the discharging tray 105 can be drawn out in a direction of arrowA2 where, in a drawn-out state, the discharging tray 105 can retaindischarged documents.

The display operation device 106 is an example of a display device andan operation device. The display operation device 106 has a displaycomposed of liquid crystal, organic EL (Electro-Luminescence), etc., andan interface circuit that outputs image data on the display so as todisplay image data on the display. The display operation device 106further includes a touch-panel style input device and an interfacecircuit that acquires signals from the input device so as to receive anoperation by a user and output signals according to an input by theuser. Note that a display device and an operation device may beseparately provided.

FIG. 2 is a view for illustrating a conveyance path inside the imagereading apparatus 100.

The conveyance path inside the image reading apparatus 100 includes: afirst sensor 111, feed rollers 112 a, 112 b, retard rollers 113 a, 113b, an open/close sensor 114, first conveyance rollers 115 a, 115 b,first driven rollers 116 a, 116 b, a second sensor 117, a first imagingunit 118 a, a second imaging unit 118 b, a third sensor 119, secondconveyance rollers 120 a, 120 b, and second driven rollers 121 a, 121 b.

Hereinafter, the feed rollers 112 a, 112 b may be collectively referredto as the feed roller 112. Likewise, the retard rollers 113 a, 113 b maybe collectively referred to as the retard roller 113. The firstconveyance rollers 115 a and 115 b may be collectively referred to asthe first conveyance roller 115. The first driven rollers 116 a and 116b may be collectively referred to as the first driven roller 116. Thesecond conveyance rollers 120 a and 120 b may be collectively referredto as the second conveyance roller 120. The second driven rollers 121 aand 121 b may be collectively referred to as the second driven roller121. The first imaging unit 118 a and the second imaging unit 118 b maybe collectively referred to as the imaging unit 118.

The lower surface of the upper housing 102 forms an upper guide 108 a ofthe document conveyance path, while the upper surface of the lowerhousing 101 forms a lower guide 108 b of the document conveyance path.In FIG. 2, an arrow A3 indicates a document conveyance direction.Hereinafter, upstream refers to upstream of the document conveyancedirection A3; downstream refers to downstream of the document conveyancedirection A3.

The first sensor 111 is a contact detecting sensor, is arranged on theupstream side of the feed roller 112 and retard roller 113 and detectswhether or not a document is placed on the document tray 103.

The open/close sensor 114 is a contact detecting sensor that detects anopen/closed state of the upper housing 102. The open/close sensor 114detects whether the upper housing 102 is open or closed in relation tothe lower housing 101 by detecting whether or not a projection 114 aequipped on the upper housing 102 is engaged with a recess 114 bequipped on the lower housing 101.

The second sensor 117 is a contact detecting sensor and is arranged onthe downstream side of the first conveyance roller 115 and first drivenroller 116, as well as, on the upstream side of the imaging unit 118.The second sensor 117 detects the presence of a document between thefirst conveyance roller 115 and first driven roller 116, and the imagingunit 118 in the document conveyance direction A3.

The third sensor 119 is a contact detecting sensor and is arranged onthe downstream side of the imaging unit 118, as well as, on the upstreamside of the second conveyance roller 120 and second driven roller 121.The third sensor 119 detects the presence of a document between theimaging unit 118, and the second conveyance roller 120 and second drivenroller 121 in the document conveyance direction A3.

A document placed on the document tray 103 is conveyed in the documentconveyance direction A3 between the upper guide 108 a and the lowerguide 108 b by the rotation of the feed roller 112 in a direction ofarrow A5. The retard roller 113 rotates in a direction of arrow A6 whena document is being conveyed. By the movement of the feed roller 112 andthe retard roller 113, when a plurality of documents is placed on thedocument tray 103, only a document being in contact with the feed roller112 among the documents placed on the document tray 103 is separated. Assuch, the feed roller 112 and retard roller 113 function as a conveyancemember that conveys a document, as well as, as a separating member thatseparates a document by limiting the conveyance of documents other thanthe separated document (multi feed prevention).

The document is fed between the first conveyance roller 115 and thefirst driven roller 116 through the guide of the upper guide 108 a andlower guide 108 b. The document is then fed between the first imagingunit 118 a and the second imaging unit 118 b by the rotation of thefirst conveyance roller 115 in a direction of arrow A7. The documentread by the imaging unit 118 is discharged on the discharging tray 105by the rotation of the second conveyance roller 120 in a direction ofarrow A8.

FIG. 3 is a perspective view of the first imaging unit 118 a seen fromthe side of the document conveyance path. Note that the second imagingunit 118 b has the same structure as the first imaging unit 118 a. FIG.4 is a view for illustrating the imaging unit 118 and a conveyancemechanism of the upstream and downstream sides of the imaging unit 118.

The first imaging unit 118 a is arranged above and opposing the secondimaging unit 118 b. The first imaging unit 118 a is equipped with animaging unit guide 122 for guiding a document between the first imagingunit 118 a and the second imaging unit 118 b. The first imaging unit 118a captures an image of the back surface of a conveyed document and thesecond imaging unit 118 b captures an image of the front surface of aconveyed document.

While the second imaging unit 118 b is fixed to the lower housing 101,the first imaging unit 118 a is supported by the upper housing 102 suchthat the first imaging unit 118 a is movable in a direction A9perpendicular to the document conveyance path. An energizing spring 123is equipped above the imaging unit guide 122 so that the energizedspring 123 energizes the first imaging unit 118 a toward the secondimaging unit 118 b.

The first imaging unit 118 a includes a first light source 124 a, afirst imaging sensor 125 a, a first white reference member 126 a, afirst transparent member 127 a, etc. The second imaging unit 118 bincludes a second light source 124 b, a second imaging sensor 125 b, asecond white reference member 126 b, a second transparent member 127 b,etc.

The first light source 124 a is provided on the opposite side of thesecond white reference member 126 b across the first transparent member127 a and the second transparent member 127 b, as well as, on theupstream side of the first imaging sensor 125 a in the documentconveyance direction A3. The first light source 124 a irradiates lighttoward the back surface of a document that has been conveyed to theposition of the imaging unit 118 (when there is no conveyed document,toward the second white reference member 126 b of the opposing secondimaging unit 118 b). The first light source 124 a is equipped with anLED (Light Emitting Diode) 128 a at an end thereof in a direction A4perpendicular to the document conveyance direction A3, and furtherequipped with a light guide member 129 a that guides light irradiatedfrom the LED along the direction A4. The light guide member 129 a isequipped with a plurality of slits 130 a along the direction A4 throughwhich light irradiated from the LED 128 a passes. The widths of theslits 130 a are increased as the slits are farther from the LED 128 a sothat the light amount becomes substantially uniform at each position.

A shield member 131 a that has an opening on the side facing the imagingposition L1 is provided around the light guide member 129 a so that thefirst light source 124 a can irradiate light toward the imaging positionL1 of the first imaging sensor 125 a. As such, the first light source124 a is provided in a manner in which the direction of the irradiatedlight is inclined with reference to the imaging direction of the firstimaging sensor 125 a.

Likewise, the second light source 124 b is provided on the opposite sideof the first white reference member 126 a across the second transparentmember 127 b and the first transparent member 127 a, as well as, on thedownstream side of the second imaging sensor 125 b in the documentconveyance direction A3. The second light source 124 b irradiates lighttoward the front surface of the document that has been conveyed to theposition of the imaging unit 118 (when there is no conveyed document,toward the first white reference member 126 a of the opposing firstimaging unit 118 a). The second light source 124 b is equipped with anLED at an end thereof in the direction A4 and further equipped with alight guide member that guides light irradiated from the LED along thedirection A4. The second light source 124 b is provided in a manner inwhich the direction of the irradiated light is inclined with referenceto the imaging direction of the second imaging sensor 125 b.

The first imaging sensor 125 a is an example of the imaging device andis provided on the opposite side of the second white reference member126 b across the first transparent member 127 a and the secondtransparent member 127 b. The first imaging sensor 125 a is a ContactImage Sensor (CIS) of a unit magnification optical system type that hasimaging elements using complementary metal oxide semiconductor (CMOS)that are linearly arranged in the main scanning direction. Further, thefirst imaging sensor 125 a has a lens that forms an image on the imagingdevice and an A/D (analog to digital) converter that amplifies theelectric signals output from the imaging device and converts the analogsignals to digital signals (A/D). At the imaging position L1, the firstimaging sensor 125 a generates and outputs a document image captured aback surface and periphery of a document that was conveyed between thefirst imaging unit 118 a and the second imaging unit 118 b, i.e.,between the second transparent member 127 b and the first imaging sensor125 a. When there is no conveyed document, the first imaging sensor 125a generates and outputs a white reference image captured the secondwhite reference member 126 b.

Likewise, the second imaging sensor 125 b, at the imaging position L2,is an example of the imaging device and is provided on the opposite sideof the first white reference member 126 a across the first transparentmember 127 a and the second transparent member 127 b. The second imagingsensor 125 b is a CIS of a unit magnification optical system type thathas imaging elements using CMOS that are linearly arranged in the mainscanning direction. Further, the second imaging sensor 125 b has a lensthat forms an image on the imaging device and an A/D converter thatamplifies the electric signals output from the imaging device andconverts the analog signals to digital signals. At the imaging positionL2, the second imaging sensor 125 b generates and outputs a documentimage captured a front surface and periphery of a document that wasconveyed between the first imaging unit 118 a and the second imagingunit 118 b, i.e., between the first transparent member 127 a and thesecond imaging sensor 125 b. When there is no conveyed document, thesecond imaging sensor 125 b generates and outputs a white referenceimage captured the first white reference member 126 a.

Note that the first imaging sensor 125 a and the second imaging sensor125 b may be an imaging sensor of an optical reduction system type thathas imaging elements using charge coupled device (CCD), instead of CMOS.

The first white reference member 126 a is provided at a position abovethe first transparent member 127 a and spaced apart from the firsttransparent member 127 a and opposing the second light source 124 b andsecond imaging sensor 125 b of the second imaging unit 118 b. Thesurface of the first white reference member 126 a facing the secondimaging sensor 125 b is white. Likewise, the second white referencemember 126 b is provided at a position below the second transparentmember 127 b and spaced apart from the second transparent member 127 band opposing the first light source 124 a and first imaging sensor 125 aof the first imaging unit 118 a. The surface of the second whitereference member 126 b facing the first imaging sensor 125 a is white.The image reading apparatus 100 can correct an image, such as by shadingcorrection, based on the image signals captured the first whitereference member 126 a and the second white reference member 126 b.

The first transparent member 127 a and the second transparent member 127b are formed of transparent glass. Note that the first transparentmember 127 a and the second transparent member 127 b may instead beformed of transparent plastic etc.

Hereinafter, the first light source 124 a and the second light source124 b may be collectively referred to as the light source 124, and thefirst imaging sensor 125 a and the second imaging sensor 125 b may becollectively referred to as the imaging sensor 125. The first whitereference member 126 a and the second white reference member 126 b maybe collectively referred to as the white reference member 126, and thefirst transparent member 127 a and the second transparent member 127 bmay be collectively referred to as the transparent member 127.

As depicted in FIG. 4, the first driven roller 116 is arranged above andopposing the first conveyance roller 115. That is, the first drivenroller 116 is arranged on the opposite side of the second whitereference member 126 b with reference to the upper surface of the secondtransparent member 127 b from the first conveyance roller 115 in thedirection A9 perpendicular to the second transparent member 127 b. Theconveyance roller pair including the first conveyance roller 115 and thefirst driven roller 116 functions as a conveyance member that conveys adocument between the first imaging unit 118 a and the second imagingunit 118 b, i.e., between the second transparent member 127 b and thefirst imaging sensor 125 a.

A position L3, which is the position of the center O₁ as an rotationaxis of the first driven roller 116 in the document conveyance directionA3, is shifted to the side of the imaging unit 118, i.e., the side ofthe first imaging sensor 125 a, than a position L4 which is the positionof the center O₂ as an rotation axis of the first conveyance roller 115in the document conveyance direction A3. A nip position L5 of the firstconveyance roller 115 and the first driven roller 116 is arranged abovethe upper surface of the second transparent member 127 b, i.e., on theopposite side of the second white reference member 126 b with referenceto the upper surface of the second transparent member 127 b in thedirection A9 perpendicular to the second transparent member 127 b.

In particular, the nip position L5 is arranged such that a position L6,at which a tangent plane P2 that contacts the first conveyance roller115 at the nip position L5 contacts the upper surface of the secondtransparent member 127 b, is arranged on the upstream side of theimaging positions L1 and L2 in the document conveyance direction A3. Assuch, the first conveyance roller 115 and the first driven roller 116can convey a document such that the document is conveyed along thesecond transparent member 127 b at the imaging positions L1 and L2.

The second driven roller 121 is arranged above and opposing the secondconveyance roller 120. That is, the second driven roller 121 is arrangedon the opposite side of the second white reference member 126 b withreference to the upper surface of the second transparent member 127 bfrom the second conveyance roller 120 in the direction A9.

A position L7, which is the position of the center O₃ as an rotationaxis of the second driven roller 121 in the document conveyancedirection A3, is shifted to the side of the imaging unit 118, i.e., theside of the first imaging sensor 125 a, than a position L8 which is theposition of the center O₄ as an rotation axis of the second conveyanceroller 120 in the document conveyance direction A3. A nip position L9 ofthe second conveyance roller 120 and the second driven roller 121 isarranged at the same height as the nip position of the first conveyanceroller 115 and the first driven roller 116 from the upper surface of thesecond transparent member 127 b in the direction A9 perpendicular to thesecond transparent member 127 b. In particular, the nip position L9 isarranged so that a position L10, at which a tangent plane P4 thatcontacts the second conveyance roller 120 at the nip position L9contacts the upper surface of the second transparent member 127 b, isarranged on the downstream side of the imaging positions L1 and L2 inthe document conveyance direction A3. The angle of the tangent plane P4with reference to the upper surface of the second transparent member 127b is preferably arranged to be the same angle of the tangent plane P2with reference to the upper surface of the second transparent member 127b.

FIG. 5 is a view for illustrating the arrangement of the firstconveyance roller 115 and the first driven roller 116.

A distance h between the nip position L5 of the first conveyance roller115 and the first driven roller 116 and an extension plane P1 of theupper surface of the second transparent member 127 b is set to be largerthan the height of an embossed bump that may be formed on a card to beconveyed. Likewise, depicted in FIG. 4, a distance between the nipposition L9 of the second conveyance roller 120 and the second drivenroller 121 and an extension plane P3 of the upper surface of the secondtransparent member 127 b is set to be larger than the height of anembossed bump that may be formed on a card to be conveyed. The height ofan embossed bump can be defined according to the specification of thedevice and may be set at 0.46 mm that is the height of embossing on anidentification (ID) card specified by ISO/IEC7811-1. Alternatively, theheight of an embossed bump may be set at 0.48 mm that is the height ofembossing on a card specified by Japanese Industrial Standards (JIS).

The following formulas can be established with regard to the firstconveyance roller 115 and the first driven roller 116:

$\begin{matrix}{{{\sin\;\theta_{1}} = \frac{\delta}{r_{1} + r_{2}}},{{\tan\;\theta_{1}} = \frac{h}{L}}} & \left\lbrack {{Math}\mspace{14mu} 1} \right\rbrack\end{matrix}$θ₁ is an angle of a straight line extending from the imaging position L2of the second imaging sensor 125 b to the nip position L5 of the firstconveyance roller 115 and the first driven roller 116 with reference tothe extension plane P1. r₁ is the radius of the first conveyance roller115 and r₂ is the radius of the first driven roller 116. L is a distancefrom the nip position L5 to the imaging position L2 of the secondimaging sensor 125 b in the document conveyance direction A3. δ is adisplacement of the center O₁ of the first driven roller 116 withreference to the center O₂ of the first conveyance roller 115 in thedocument conveyance direction A3.

Thus, the displacement δ of the center O₁ of the first driven roller 116with reference to the center O₂ of the first conveyance roller 115 inthe document conveyance direction can be calculated by the followingformula:

$\begin{matrix}{\delta = {\left( {r_{1} + r_{2}} \right) \times {\sin\left( {\tan^{- 1}\left( \frac{h}{L} \right)} \right)}}} & \left\lbrack {{Math}\mspace{14mu} 2} \right\rbrack\end{matrix}$

To arrange the position L6 depicted in FIG. 4 on the side of the firstconveyance roller 115 and first driven roller 116 than the imagingposition L2, the center O₁ of the first driven roller 116 may be shiftedby δ or more from the center O₂ of the first conveyance roller 115 inthe document conveyance direction A3. For example, when h is 1.5 mm; r₇,6.8 mm; r₂, 6.5 mm; and L, 18.7 mm, the displacement of the center O₁ ofthe first driven roller 116 with reference to the center O₂ of the firstconveyance roller 115 is set at 1.1 mm.

FIG. 6 is a view for illustrating how a document is conveyed.

In FIG. 6, the path R1 indicates an ideal conveyance path through whichthe leading end of a document passes. The leading end of a document thatis conveyed by the image reading apparatus 100 contacts the firstconveyance roller 115 at a position L11, and proceeds upward from theextension plane P1 on the upper surface of the second transparent member127 b along the tangent plane P6 of the first conveyance roller 115.Then, the leading end of the document contacts the guide member 122 a ofthe imaging unit guide 122 at a position L13, then, proceeds downward.

The leading end of the document that is directed downward by the guidemember 122 a is fed between the first conveyance roller 115 and thefirst driven roller 116. The leading end of the document passes throughthe nip position L5 of the first conveyance roller 115 and the firstdriven roller 116, proceeds along the tangent plane P2 at the nipposition L5, and contacts the second transparent member 127 b of thesecond imaging unit 118 b at the position L6.

The leading end of the document that has contacted the secondtransparent member 127 b is conveyed along the second transparent member127 b. After passing through between the first imaging unit 118 a andthe second imaging unit 118 b, the leading end of the document proceedsalong the extension plane P3 of the upper surface of the secondtransparent member 127 b and contacts the second conveyance roller 120at a position L14. The leading end of the document that has contactedthe second conveyance roller 120 proceeds along the tangent plane P7 ofthe second conveyance roller 120 at the position L14, and contacts thesecond driven roller 121 at a position L15.

The leading end of the document that has contacted the second drivenroller 121 is fed between the second conveyance roller 120 and thesecond driven roller 121, and passes through the nip position L9 of thesecond conveyance roller 120 and the second driven roller 121.

When the leading end of the document has passed the nip position L9, aportion of the document located on the second transparent member 127 bis pulled along the tangent plane P4 at the nip position L9 andseparated from the second transparent member 127 b on the downstreamside of the position L10 in the document conveyance direction A3. Thedocument is always maintained at a certain distance from the secondtransparent member 127 b at the imaging positions L1 and L2, and thedistance from the document to each imaging sensor 125 is constant. Assuch, even when CIS of a unit magnification optical system type withsmall depth-of-field is used, occurrence of divergence of focus can beprevented and the imaging sensor 125 can acquire stable images. Inparticular, as a distance from a document to each imaging sensor 125 inthe direction A4 (main scanning direction) perpendicular to the documentconveyance direction A3 is constant, occurrence of unevenness in thehorizontal direction in the document image is prevented. By stabilizingthe conveyance path of a document, the image reading apparatus 100 doesnot need an ample space in the direction A9 (vertical direction)perpendicular to the second transparent member 127 b, and the devicesize can be reduced.

Since the leading end of a document is conveyed along the secondtransparent member 127 b, the leading end of the document can clean thesecond transparent member 127 b, i.e., remove dirt substances from thesecond transparent member 127 b. Although dirt substances may not onlyadhere to the second transparent member 127 b but also possibly adhereto the first transparent member 127 a, dirt substances adhering to thefirst transparent member 127 a are more likely to fall by its own weightand adhere to the second transparent member 127 b. In the image readingapparatus 100, the conveyance of the leading end of a document along thesecond transparent member 127 b allows removal of dirt substances thatfell from the first transparent member 127 a.

FIG. 7 is a view for illustrating the arrangement of the first lightsource 124 a and the first imaging sensor 125 a.

As depicted in FIG. 7, the first light source 124 a is provided on theupstream side of the first imaging sensor 125 a in the documentconveyance direction A3 such that the light irradiation direction A10 isinclined with reference to the imaging direction A11 of the firstimaging sensor 125 a. The second white reference member 126 b isprovided spaced apart from the second transparent member 127 b. As such,when a document D conveyed on the second transparent member 127 b hasreached immediately before the imaging position L1 of the first imagingsensor 125 a, a shadow of the leading end of the document D is formed onthe second white reference member 126 b at the imaging position L1.

When a dirt substance (foreign substance), such as paper dust, otherfine particles, glue, etc., adheres to the transparent member 127, noiseline (vertical streak noise) extending in a document conveyancedirection (sub-scanning direction) is generated in a document image,necessitating removal of such noise line. Dirt substances may in somecases be captured in white and in other cases in black in the documentimage. When the color of a dirt substance is similar to the color of abackground of a document, the dirt substance is less likely to beidentified or detected in the document image. In addition, since thewhite reference member 126 is white, although black dirt substances canbe clearly identified and accurately detected in the white referenceimage, white dirt substances are less likely to be identified anddetected in the white reference image. Thus, the image processing system1 detects noise line in a shadow region formed by the shadow of adocument in the correction image that was made based on the documentimage. Since the shadow formed on the white reference member 126 is graythat is an intermediate color of white and black, both white and blackdirt substances can be identified and accurately detected in the shadowregion.

The correction image preferably has a shadow of 4 pixels or more in thedocument conveyance direction A3 so that the noise line can be welldetected in the correction image. Accordingly, the width a of a shadowin the document conveyance direction A3 formed on the second whitereference member 126 b is preferably a length equivalent to 4 pixels(0.3 mm in 300 dpi) or more.

The width a is the product of a distance b from the upper surface of thesecond transparent member 127 b to the upper surface of the second whitereference member 126 b and the tangent of an angle θ of the lightirradiation direction A10 with reference to the imaging direction A11.In order to increase the width a, the angle θ or the distance b shouldbe increased. However, if the angle θ is excessively increased, thedimension of the imaging unit 118 is enlarged. As such, the angle θ ispreferably a value between 30° or more and 45° or less. Whereas, if thelength b is excessively increased, the luminance of the second whitereference member 126 b becomes lower (darker) in the white referenceimage captured the second white reference member 126 b, and it becomesdifficult to perform satisfactory shading correction using the whitereference image. As such, the length b is preferably a value between 0.8mm or more and 1.8 mm or less.

Each imaging unit 118 is constituted by a CIS and irradiates the secondwhite reference member 126 b only by the directive light emitted fromthe first light source 124 a. For example, if an image reading apparatushas a reflection member that reflects light emitted from the first lightsource 124 a toward the second white reference member 126 b, thedimension of the device increases, as well as, a shadow formed on thesecond white reference member 126 b becomes bright and disappears(fades). Whereas, the image reading apparatus 100 does not have areflection member that reflects the light emitted from the first lightsource 124 a toward the side of the second white reference member 126 b.In this way, with the image reading apparatus 100, the dimension of thedevice can be reduced, as well as, a shadow can be favorably formed onthe second white reference member 126 b.

Note that the second light source 124 b is provided on the downstreamside of the second imaging sensor 125 b in the document conveyancedirection A3 such that the light irradiation direction is inclined withreference to the imaging direction of the second imaging sensor 125 b.The first white reference member 126 a is provided spaced apart from thefirst transparent member 127 a. As such, when the rear end of a documentD conveyed on the second transparent member 127 b has passed the imagingposition L2 of the second imaging sensor 125 b, a shadow of the rear endof the document D is formed at the imaging position L2 on the firstwhite reference member 126 a.

When the light source 124 is provided on the upstream side of theimaging sensor 125 in the document conveyance direction A3, a shadow isformed by the leading end of the document D, while, when the lightsource 124 is provided on the downstream side of the imaging sensor 125,a shadow is formed by the rear end of the document D. A shadow formed bythe leading end of the document D allows detection of a shadow area fromthe document image and detection of a dirt substance before completionof the conveyance of the document D, thus, the light source 124 ispreferably provided on the upstream side of the imaging sensor 125 inthe document conveyance direction A3.

As described above, since a sufficiently long shadow is formed on eachwhite reference member 126 in the image reading apparatus 100, the imageprocessing system 1 can accurately detect both black and white dirtsubstances at the imaging position of each imaging sensor 125.

In addition, as described above, the first conveyance roller 115 and thefirst driven roller 116 can convey a document such that the document isconveyed along the second transparent member 127 b at the imagingpositions L1 and L2. In this way, in contrast to a case where a documentis conveyed floated in the air without being conveyed along a specificmember, the image reading apparatus 100 can stabilize a documentconveyance path regardless of the kind of document (thickness, hardness,etc.) and stably generate a shadow on the white reference member 126.

Further, the image reading apparatus 100 has a transparent member 127between the document conveyance path and each white reference member126, protecting the white reference member 126 and preventing the whitereference member 126 from dirt or scratches. Since the transparentmember 127 has higher rigidity than the white reference member 126, thetransparent member 127 is less likely to sustain scratches when cleanedby users.

FIG. 8 is a block diagram depicting schematic components of the imagereading apparatus 100 and the information processing apparatus 200.

In addition to the above-described components, the image readingapparatus 100 further includes a driving device 134, a first interfacedevice 135, a first storage device 140, a first Central Processing Unit(CPU) 160, a first processing circuit 180, etc.

The driving device 134 includes one or a plurality of motors and rotatesthe feed roller 112, the retard roller 113, the first conveyance roller115, and the second conveyance roller 120 according to a control signalfrom the CPU 160 to convey a document.

The first interface device 135 has an interface circuit conforming to aserial bus such as Universal Serial Bus (USB). The first interfacedevice 135 transmits and receives various images and information througha communication connection with the information processing apparatus200. Instead of the first interface device 135, a communication devicethat has an antenna for transmitting and receiving wireless signals anda wireless communication interface circuit for transmitting andreceiving signals via a wireless communication channel according to apredetermined communication protocol may be used. The predeterminedcommunication protocol may be, for example, a wireless local areanetwork (LAN).

The first storage device 140 includes: a memory device, such as a randomaccess memory (RAM) and a read only memory (ROM); a fixed disk device,such as a hard disk; or a portable storage device, such as a flexibledisk and an optical disk. The first storage device 140 stores a computerprogram, a database, a table, etc., that are used for various processingof the image reading apparatus 100. The computer program may beinstalled on the first storage device 140 from a computer-readable,non-transitory medium such as a compact disk read only memory (CD-ROM),a digital versatile disk read only memory (DVD-ROM), etc., by using awell-known setup program, etc.

The first storage device 140 further stores a variety of images. Thefirst storage device 140 also stores number of documents which have beenscanned as a document scan count, the position of dirt, etc. The scancount is the number of times the image reading apparatus 100 has scanneda document and incremented each time the image reading apparatus 100scans a document. The position of dirt is a position where a dirtsubstance is detected in the white reference image. The scan count andthe position of dirt are stored in a non-transitory memory to bereferred to even after the power of the image reading apparatus 100 isswitched off and on again.

The first CPU 160 operates according to a program stored in advance inthe first storage device 140. Note that a digital signal processor(DSP), a large scale integration (LSI), etc., may be used instead of thefirst CPU 160. Alternatively, an Application Specific Integrated Circuit(ASIC), a field-programming gate array (FPGA) etc., may be used insteadof the first CPU 160.

The first CPU 160 is connected to the display operation device 106, thefirst sensor 111, the open/close sensor 114, the second sensor 117, thethird sensor 119, the imaging unit 118, the driving device 134, thefirst interface device 135, the first storage device 140, the firstprocessing circuit 180, etc., and controls these components. The firstCPU 160 controls driving of the driving device 134, document reading ofthe imaging unit 118, etc., to acquire a document image.

The first processing circuit 180 performs predetermined image processingsuch as correction processing on the document image acquired from theimaging unit 118. Note that a LSI, a DSP, an ASIC, a FPGA, etc., may beused as the first processing circuit 180.

Whereas, the information processing apparatus 200 further includes adisplay device 201, an operation device 202, a second interface device203, a second storage device 220, a second CPU 240, a second processingcircuit 260, etc.

The display device 201 is an example of a display device, which has adisplay composed of liquid crystal, organic EL, etc., and an interfacecircuit for outputting image data on the display and displays image dataon the display according to an instruction from the second CPU 240.

The operation device 202 is an example of an operation device, whichfurther includes an input device and an interface circuit that acquiressignals from the input device, receives an operation by a user, andoutputs signals according to the input by the user to the second CPU240.

The second interface device 203 includes an interface circuit or awireless communication interface circuit, similar to the one of thefirst interface device 135, and transmits and receives a variety ofimages and information through a communication connection with the imagereading apparatus 100.

The second storage device 220 has: a memory device, such as a RAM and aROM; a fixed disk device, such as a hard disk; or a portable storagedevice, such as a flexible disk and an optical disk. Further, the secondstorage device 220 stores a computer program, a database, a table, etc.,that are used for various processing of the information processingapparatus 200. The computer program may be installed on the secondstorage device 220 from a computer-readable, non-transitory medium suchas a CD-ROM, a DVD-ROM, etc., by using a well-known setup program, etc.

The second storage device 220 further stores a variety of images. Thesecond storage device 220 also stores noise line positions etc. Thenoise line position is a position where a noise line is detected in acorrection image. The noise line position is stored in a non-transitorymemory, a hard disk, etc., so as to be referred to even after the powerof the information processing apparatus 200 is switched off and onagain.

The second CPU 240 operates according to a program stored in advance inthe second storage device 220. Note that a DSP, a LSI, an ASIC, a FPGA,etc., may be used instead of the second CPU 240.

The second CPU 240 is connected to the display device 201, the operationdevice 202, the second interface device 203, the second storage device220, the second processing circuit 260, etc., and controls thesecomponents. The second CPU 240 controls the components and executesimage processing on images acquired from the image reading apparatus100.

The second processing circuit 260 performs predetermined imageprocessing such as correction processing on an image acquired from theimage reading apparatus 100. Note that a DSP, a LSI, an ASIC, a FPGA,etc., may be used as the second processing circuit 260.

FIG. 9 is a view depicting the schematic components of the first storagedevice 140 and the first CPU 160 of the image reading apparatus 100.

As depicted in FIG. 9, the first storage device 140 stores programs,such as a first image acquiring program 141, a first dirt substancedetection processing program 142, a correction data generation program149, a correction image generation program 150, etc. The first dirtsubstance detection processing program 142 includes a first resultacquiring program 143, a dirt degree calculation program 144, anotifying program 145, a setting program 146, a threshold acquiringprogram 147, an information acquiring program 148, etc. Each program isa functional module implemented by software that operates on theprocessor. The first CPU 160 reads each program stored in the firststorage device 140 and operates according to the read program. As such,the first CPU 160 functions as a first image acquiring module 161, afirst dirt substance detection processing module 162, a first resultacquiring module 163, a dirt degree calculation module 164, a notifyingmodule 165, a setting module 166, a threshold acquiring module 167, aninformation acquiring module 168, a correction data generation module169, and a correction image generation module 170.

FIG. 10 is a view depicting the schematic components of the secondstorage device 220 and second CPU 240 of the information processingapparatus 200.

As depicted in FIG. 10, the second storage device 220 stores programs,such as a second image acquiring program 221, a second dirt substancedetection processing program 222, a determination program 230, acorrection program 231, etc. The second dirt substance detectionprocessing program 222 includes a second result acquiring program 223, adevice information acquiring program 224, an edge pixel extractingprogram 225, a document region detecting program 226, a shadow regiondetecting program 227, a noise pixel extracting program 228, a noiseline detecting program 229, etc. Each program is a functional moduleimplemented by software that operates on the processor. The second CPU240 reads each program stored in the second storage device 220 andoperates according to the read program. As such, the second CPU 240functions as a second image acquiring module 241, a second dirtsubstance detection processing module 242, a second result acquiringmodule 243, a device information acquiring module 244, an edge pixelextracting module 245, a document region detecting module 246, a shadowregion detecting module 247, a noise pixel extracting module 248, anoise line detecting module 249, a determination module 250 and acorrection module 251.

FIG. 11 is a flowchart depicting an example of the operation of theoverall processing of the image reading apparatus 100. The followingwill describe an example of the operation of the overall processing ofthe image reading apparatus 100 with reference to the flowchart depictedin FIG. 11. Note that the operation flow as will be described below isperformed primarily by the first CPU 160 jointly with each component ofthe image reading apparatus 100 according to programs prestored in thefirst storage device 140. This operation flow is performed immediatelyafter start-up of the device or after document reading processing.

First, the first image acquiring module 161 causes each imaging sensor125 to capture an image of each white reference member 126 to generate awhite reference image and acquires the generated white reference image(step S101). The white reference image is an image where the number ofpixels in a vertical direction (a document conveyance direction A3) isone and a plurality of pixels are arranged in a horizontal direction (adirection A4 perpendicular to the document conveyance direction A3).Hereinafter, the white reference image captured the second whitereference member 126 b by the first imaging sensor 125 a may be referredto as the first white reference image, and the white reference imagecaptured the first white reference member 126 a by the second imagingsensor 125 b may be referred to as the second white reference image.

Next, the first result acquiring module 163 of the first dirt substancedetection processing module 162 acquires a second result from theinformation processing apparatus 200 via the first interface device 135(step S102). The second dirt substance detection processing module 242of the information processing apparatus 200 executes second processingfor detecting a dirt substance from the correction image. In particular,in the second processing, the second dirt substance detection processingmodule 242 detects a dirt substance causing noise line from thecorrection image. The second result is a dirt substance detection resultof the second processing by the second dirt substance detectionprocessing module 242 and is a noise line detection result from thecorrection image. The second result includes information, such as,whether or not a dirt substance is detected from the correction image,the position of the detected dirt substance in the correction image, andwhether or not the detected dirt substance has been confirmed by a user.Note that, when the second dirt substance detection processing module242 has not performed the second processing, the first dirt substancedetection processing module 162 does not acquire the second result.

Next, the first dirt substance detection processing module 162 executesthe first processing (step S103). The first dirt substance detectionprocessing module 162 detects a dirt substance from the white referenceimage in the first processing. In particular, the first dirt substancedetection processing module 162 detects a dirt substance that causesdirt at an imaging position from the white reference image in the firstprocessing. Further, when the first dirt substance detection processingmodule 162 has detected a dirt substance from the white reference imagein the first processing, the first dirt substance detection processingmodule 162 determines whether the detected dirt substance is on thetransparent member on the side of the imaging sensor which captured thewhite reference image or on the transparent member on the side of thewhite reference member which was captured in the white reference image.The details of the first processing will be described later.

Next, the correction data generation module 169 generates data forshading correction based on the white reference image (step S104). Thecorrection data generation module 169 uses, for example, as the data forshading correction, an image that has a gradient value of each pixelobtained by adding a predetermined offset value to or subtracting apredetermined offset value from the gradient value of a correspondingpixel in the white reference image. The gradient value is, for example,a luminance value. Note that the gradient value may instead be a colorvalue (R value, G value, B value) etc. Note that the correction datageneration module 169 may use the white reference image as is as datafor shading correction. Hereinafter, the data for shading correctiongenerated from the first white reference image may be referred to as thefirst data for shading correction and the data for shading correctiongenerated from the second white reference image may be referred to asthe second data for shading correction.

Next, when, in the first processing, the correction data generationmodule 169 determines that a dirt substance detected from a whitereference image is on the transparent member on the side of the whitereference member which was captured in the white reference image, thecorrection data generation module 169 adjusts the data for shadingcorrection generated from the white reference image (step S105). Thecorrection data generation module 169, for example, adjusts the data forshading correction by replacing a gradient value of each pixel includedin a dirt substance region corresponding to a dirt substance in the datafor shading correction with an average value of the gradient values ofpixels included in a region of a predetermined width adjacent to thedirt substance region. Whereas, when a dirt substance is not detectedfrom the white reference image in the first processing, or when a dirtsubstance is determined to be on the transparent member on the side ofthe imaging sensor which captured the white reference image, thecorrection data generation module 169 does not adjust the data forshading correction generated from the white reference image.

When a position of a dirt substance is on the transparent member on theside of the white reference member, the dirt substance is captured inthe white reference image captured the white reference member, but thedirt substance is not captured in the document region of a documentimage, as there is a document between the imaging sensor and the dirtsubstance when the document image is captured. Thus, the document imagecan be appropriately corrected through shading correction by removingelements corresponding to a dirt substance from the data for shadingcorrection generated based on the white reference image captured thedirt substance.

Whereas, when the position of a dirt substance is on the transparentmember on the side of the imaging sensor, the dirt substance is capturedat the corresponding position in both white reference image captured bythe imaging sensor and document image subsequently captured by theimaging sensor. Thus, by performing shading correction using data forshading correction generated based on the white reference image capturedthe dirt substance as it is, the dirt substance captured in the documentimage can be removed and occurrence of noise line caused by the dirtsubstance in the correction image can be prevented.

Next, the first dirt substance detection processing module 162 executesconfirmation processing (step S106). In the confirmation processing, thefirst dirt substance detection processing module 162 determines whethera confirmation operation by a user has been received. The details of theconfirmation processing will be described later.

Next, the first image acquiring module 161 determines whether a user hasinstructed reading of a document using the display operation device 106and a reading instruction signal that instructs reading of a documenthas been received via the display operation device 106 (step S107). Whena reading instruction signal has not been received yet, the first dirtsubstance detection processing module 162 returns the processing to stepS106 and re-executes the confirmation processing.

Whereas, when a reading instruction signal has been received, the firstimage acquiring module 161 determines whether a document is placed onthe document tray 103 based on a signal received from the first sensor111 (step S108). When a document is not placed on the document tray 103,the first dirt substance detection processing module 162 returns theprocessing to step S106 and re-executes the confirmation processing.

Whereas, when a document is placed on the document tray 103, the firstimage acquiring module 161 drives the driving device 134 to rotate thefeed roller 112, retard roller 113, first conveyance roller 115 andsecond conveyance roller 120 to convey the document (step S109).

Next, the first image acquiring module 161 causes the imaging sensor 125to capture an image of the document to generate a document image,acquires the generated document image, and increments the scan countstored in the first storage device 140 (step S110). When the imagereading apparatus 100 detects dirt, the image reading apparatus 100generates and provides a warning to a user. However, the image readingapparatus 100 captures the document even if a user has not completed theconfirmation. In this way, the image reading apparatus 100 can continuecapturing an image of a document when a user does not care about thedirt, thereby improving user convenience. Hereinafter, the documentimage captured by the first imaging sensor 125 a may be referred to asthe first document image and the document image captured by the secondimaging sensor 125 b may be referred to as the second document image.

Next, the correction image generation module 170 performs shadingcorrection on the document image using the data for shading correctionbased on the white reference image to generate a correction image (stepS111). The correction image is an example of an input image. Thecorrection image generation module 170 performs shading correction onthe first document image using the first data for shading correction andperforms shading correction on the second document image using thesecond data for shading correction. Hereinafter, the correction imageobtained by correcting the first document image may be referred to asthe first correction image and the correction image obtained bycorrecting the second document image may be referred to as the secondcorrection image.

Next, the correction image generation module 170 transmits thecorrection image, first result, and device information to theinformation processing apparatus 200 via the first interface device 135(step S112). The first result is a dirt substance detection result ofthe first processing by the first dirt substance detection processingmodule 162 and is a dirt detection result at the imaging position in thewhite reference image. The first result includes information, such as,whether or not a dirt substance is detected from the white referenceimage, the position of the detected dirt substance in the whitereference image, and whether or not the detected dirt substance has beenconfirmed by a user.

The device information indicates the arrangement of the imaging sensor125 and the light source 124 in the image reading apparatus 100 thatgenerates a correction image. For example, the device informationindicates that, with regard to a first correction image, the first lightsource 124 a is provided on the upstream side of the first imagingsensor 125 a in the document conveyance direction A3 and, with regard toa second correction image, the second light source 124 b is provided onthe downstream side of the second imaging sensor 125 b in the documentconveyance direction A3. Note that the correction image generationmodule 170 may transmit the first result, only when new first result wasacquired, and may omit transmission of the first result that has alreadybeen transmitted. Further, when the device information has already beentransmitted, the correction image generation module 170 may also omittransmission of the device information.

Next, the first CPU 160 determines whether there is any documentremaining on the document tray 103 based on the signals received fromthe first sensor 111 (step S113).

When there is a document remaining on the document tray 103, the firstCPU 160 returns the processing to step S109 and repeats the processingof steps S109 to S113. Whereas, when no document is remaining on thedocument tray 103, the first CPU 160 ends the set of processing.

FIG. 12 is a flowchart depicting an example of the operation of thefirst processing. The first processing depicted in FIG. 12 is carriedout at step S103 of the flowchart depicted in FIG. 11.

First, the dirt degree calculation module 164 calculates a dirt degreeat the imaging position for each pixel included in a white referenceimage (step S201). The dirt degree is the degree of dirt caused by adirt substance, such as paper dust, on the first transparent member 127a and the second transparent member 127 b at the imaging position of theimaging sensor 125. The dirt degree calculation module 164 calculates adirt degree by comparing the gradient value of each pixel with thegradient values of peripheral pixels of the pixel of interest. Theperipheral pixels may be, for example, pixels located within apredetermined range (for example, 3 pixels) from the pixel of interest.The dirt degree calculation module 164 calculates, for example, theabsolute value of a difference between the gradient value of the pixelof interest and the average value of the gradient values of theperipheral pixels as a dirt degree of the pixel of interest. Note thatthe dirt degree calculation module 164 may calculate the absolute valueof a difference between the gradient value of the pixel of interest andthe weighted average value of the gradient values of the peripheralpixels that are weighted such that the weight becomes larger as closerto the pixel of interest, as a dirt degree of the pixel of interest.

FIG. 13 is a schematic view depicting an example of a white referenceimage.

The horizontal axis in FIG. 13 indicates the position of each pixel in ahorizontal direction in the white reference image and the vertical axisindicates the gradient value of each pixel. The surface of the whitereference member 126 facing the imaging sensor 125 is white, and, asdepicted in FIG. 13, the gradient values of pixels at horizontalpositions in the white reference image are substantially constant.However, when a dirt substance adheres to the transparent member 127,pixels 1301-1303 corresponding to the dirt substance become dark, andthe gradient values of the pixels 1301-1303 become lower compared withthe gradient values of the peripheral pixels 1304-1306. As such, thedirt degree calculation module 164 can accurately detect a dirtsubstance on the transparent member 127 by comparing the gradient valueof each pixel with the gradient values of the peripheral pixels of thepixel of interest.

Alternatively, the dirt degree calculation module 164 may calculate adirt degree by comparing the gradient value of each pixel with areference value. In such a case, the dirt degree calculation module 164calculates the absolute value of a difference between the gradient valueof the pixel of interest and a preset reference value (for example, 255)as a dirt degree of the pixel of interest.

Next, the notifying module 165 determines whether severe dirt exists atthe imaging position (step S202). When the dirt degree of any pixelcalculated with regard to the white reference image is equal to or moreof a first threshold, the notifying module 165 determines that there issevere dirt at the imaging position on the transparent member 127corresponding to the pixel. Whereas, when the dirt degree of every pixelis less than a first threshold, the notifying module 165 determines thatthere is no severe dirt at the imaging position on the transparentmember 127.

When the notifying module determines that there is no severe dirt at theimaging position, the notifying module 165 determines whether there ismoderate dirt at the imaging position (step S203). When the dirt degreeof any pixel calculated with regard to the white reference image is lessthan the first threshold and equal to or more than a third threshold,the notifying module 165 determines that there is moderate dirt at theimaging position on the transparent member 127 corresponding to thepixel. Whereas, when the dirt degree of every pixel is less than thethird threshold, the notifying module 165 determines that there is nomoderate dirt at the imaging position on the transparent member 127. Thethird threshold is set smaller than the first threshold and larger thanthe second threshold as will be described later.

When the notifying module determines that there is no moderate dirt atthe imaging position, the notifying module 165 determines whether thereis minor dirt at the imaging position (step S204). When the dirt degreeof any pixel calculated with regard to the white reference image is lessthan the third threshold and equal to or more than a second threshold,the notifying module 165 determines that there is minor dirt at theimaging position on the transparent member 127 corresponding to thepixel. Whereas, when the dirt degree of every pixel is less than asecond threshold, the notifying module 165 determines that there is nominor dirt at the imaging position on the transparent member 127. Thesecond threshold is set at a smaller value than the first threshold andthe third threshold.

When the notifying module 165 determines that there is no minor dirt atthe imaging position, the notifying module 165 ends the set of stepswithout generating and providing the warning to a user (step S205).

Whereas, when the notifying module 165 determines that there is severeor moderate dirt at the imaging position, the notifying module 165stores the position of a pixel corresponding to the dirt as a dirtposition in the first storage device 140 (steps S206, S207). In otherwords, when the notifying module 165 detects a dirt substance causingsevere or moderate dirt, the notifying module 165 stores the positionwhere the dirt substance is detected in the white reference image as adirt position in the first storage device 140. The notifying module 165stores the position of a pixel of which calculated dirt degree is equalto or more than the third threshold as a dirt position.

Whereas, when the notifying module 165 determines that there is nosevere or moderate dirt but there is minor dirt at the imaging position,the notifying module 165 determines whether the position of a pixelcorresponding to the minor dirt is stored in the first storage device140 as a dirt position (step S208).

When the position of the pixel corresponding to the minor dirt is notstored as a dirt position, i.e., the dirt has not previously beendetected as moderate dirt or severe dirt, the notifying module 165 doesnot generate and provide the warning to a user (step S205) and ends theset of steps. Whereas, when the position of the pixel corresponding tothe minor dirt is stored as a dirt position, i.e., the dirt haspreviously been detected as moderate dirt or severe dirt, the notifyingmodule 165 transfers the processing to step S210 in order to processesfor the minor dirt in the same way as moderate dirt.

Next, the notifying module 165 determines whether the dirt is newlygenerated dirt (steps S209, S210). The notifying module 165 determinesthat the dirt is newly generated dirt when the position of a specificpixel corresponding to the dirt is not stored in the first storagedevice 140 as a dirt position, or determines that the dirt is theexisting dirt when the position is stored. Note that the notifyingmodule 165 may keep counting the number of detected dirt specks, and,when the number of detected dirt specks that is detected this time islarger than that of previous time, the notifying module 165 maydetermine that the dirt is newly generated dirt.

When the dirt is newly generated dirt, the notifying module 165 sets thescan count stored in the first storage device 140 to a predeterminedvalue (steps S211, S212). The notifying module 165 sets a value that isequal to or more than a scan count threshold as a predetermined value.The scan count threshold is a threshold to be compared with the scancount when there is moderate dirt at the imaging position, and thenotifying module 165 generates and provides the warning to a user onlywhen the scan count exceeds the scan count threshold. By setting thescan count to a value that is equal to or more than the scan countthreshold, the image reading apparatus 100 can immediately generate andprovide the warning again when the dirt is detected again without havingbeen confirmed by a user.

When there is moderate dirt at the imaging position (or there is minordirt that has been previously detected as moderate or severe dirt), thenotifying module 165 sets a scan count threshold (step S213). Thenotifying module 165, for example, changes the scan count thresholdaccording to the number of detected moderate or minor dirt specks, i.e.,the number of pixels of which dirt degree is less than the firstthreshold and equal to or more than the second threshold. The notifyingmodule 165 changes the scan count threshold so that the scan countthreshold becomes smaller as the number of pixels of which dirt degreeis less than the first threshold and equal to or more than the secondthreshold is larger. For example, when the number of pixels of whichdirt degree is less than the first threshold and equal to or more thanthe second threshold is larger than a first predetermined value, thenotifying module 165 sets the scan count threshold at an average valueof scan counts per day. Whereas, when the number of pixels of which dirtdegree is less than the first threshold and equal to or more than thesecond threshold is smaller than a second predetermined value that issmaller than the first predetermined value, the notifying module 165sets the scan count threshold at an average value of scan counts perweek. As the average value of scan counts, the average value with regardto this image reading apparatus 100 may be used or the average value ofscan counts by general users that are acquired from a plurality of imagereading apparatuses may be used.

In this way, the notifying module 165 can increase the frequency ofgenerating and providing the warning to a user to prompt cleaning whenthe number of moderate dirt and minor dirt is large, or can decrease thefrequency of generating and providing the warning to a user to suppresstroubling a user when the number of moderate and minor dirt is small.

Note that the notifying module 165 may change the scan count thresholdaccording to the number of pixels of which dirt degree is equal to ormore than the second threshold, the number of pixels of which dirtdegree is equal to or more than the third threshold, or the number ofpixels of which dirt degree is less than the first threshold and equalto or more than the second threshold. In such a case, the notifyingmodule 165 changes the scan count threshold so that the scan countthreshold becomes smaller as the number of such pixels is larger.Alternatively, the notifying module 165 may omit the processing of stepS213 and use a fixed value that was set as the scan count threshold inadvance.

Next, the notifying module 165 determines whether the scan count exceedsthe scan count threshold (step S214). When the scan count exceeds thescan count threshold, the notifying module 165 transfers the processingto step S216 in order to process for the moderate dirt (or minor dirtthat has been previously detected as moderate or severe dirt) in thesame way as severe dirt.

Whereas, when the scan count is equal to or less than the scan countthreshold, the notifying module 165 determines whether a dirt substancehas been detected at a position corresponding to the dirt position inthe second processing based on the second result (step S215).

When no dirt substance has been detected at a position corresponding tothe dirt position in the second processing, the notifying module 165ends the set of steps without notifying a warning to a user (step S205).Whereas, when a dirt substance has been detected at a positioncorresponding to the dirt position in the second processing, the dirt islikely to cause noise line in the correction image. In such a case, thenotifying module 165 treats the moderate dirt (or minor dirt that haspreviously been detected as moderate or severe dirt) in the same way assevere dirt and transfers the processing to step S216. In this case, awarning is notified to a user in the processing described later. Assuch, the notifying module 165 changes timing of generating andproviding the warning to a user based on the second result when thenotifying module 165 has detected a dirt substance causing dirt. Thenotifying module 165 generates and provides the warning at an earlierstage when there is dirt causing noise line in the correction image,yet, does not generate and provide the warning so as not to trouble auser when the dirt does not affect the correction image.

Note that the notifying module 165 may omit the processing of step S215and may not generate and provide the warning to a user when the scancount is equal to or less than the scan count threshold, regardless ofthe second result by the second processing.

Next, the notifying module 165 determines whether a user has alreadyconfirmed the dirt (step S216). When the display operation device 106has received a confirmation operation by a user after a warning on thedirt had previously been notified to a user, the notifying module 165determines that the user has already confirmed the dirt. Further, thenotifying module 165 may also determine that the user has alreadyconfirmed the dirt, when the second result indicates that a dirtsubstance has been detected and the position of the detected dirtsubstance in the correction image corresponds to the present dirtposition, as well as, the detected dirt substance has already beenconfirmed by a user. Note that when a difference between the horizontalposition where a dirt substance is detected in the correction image andthe horizontal position where dirt is detected in the white referenceimage is within a predetermined range, the notifying module 165recognizes that these positions correspond to each other.

When a user has already confirmed the dirt, the notifying module 165ends the set of steps without generating and providing the warning to auser (step S205). As such, when a user has already confirmed a dirtsubstance in the information processing apparatus 200, the notifyingmodule 165 does not generate and provide the warning.

Whereas, when a user has not confirmed the dirt, the notifying module165 determines whether the dirt substance causing the dirt is present onthe side of the imaging sensor or on the side of the white referencemember using the second result (step S217). That is, the notifyingmodule 165 determines whether the dirt substance is on the transparentmember on the side of the imaging sensor which captured the whitereference image or on the transparent member on the side of the whitereference member which was captured in the white reference image. When anoise line has been detected at a position corresponding to the presentdirt position within the document region in the correction image, thedirt is likely to exist on front side of the document as seen from theside of the imaging sensor, and, when a noise line has not been detectedat the position, the dirt is likely to exist on back side of thedocument as seen from the side of the imaging sensor. Thus, when thesecond result indicates that a dirt substance causing a noise line hasbeen detected in the document region of the correction image and theposition where the dirt substance has been detected in the correctionimage and the present dirt position correspond to each other, thenotifying module 165 determines that the dirt substance is on the sideof the imaging sensor. Whereas, when the second result indicates that nodirt substance causing a noise line has been detected in the documentregion of the correction image or the position where a dirt substancehas been detected in the correction image and the present dirt positiondo not correspond to each other, the notifying module 165 determinesthat the dirt substance is on the side of the white reference member.

The first dirt substance detection processing module 162, when itdetects a dirt substance, can use the second result to accuratelydetermine whether the position where the dirt substance exists is on theside of the white reference member or on the side of the imaging sensor.

Next, the notifying module 165 generates and provides the warning to auser and ends the set of steps (step S218). The notifying module 165displays an image for providing a warning on the display operationdevice 106. Note that the notifying module 165 may provide a warning byturning on an LED (not shown) or outputting voice from a speaker (notshown) etc.

FIG. 14A is a schematic view depicting an example of the receptionscreen 1400 displayed on the display operation device 106.

The reception screen depicted in FIG. 14A displays a read button 1401, aconfirm button 1402, a set button 1403, etc. The read button 1401 is abutton for instructing reading of a document; when the read button 1401is pressed, the display operation device 106 outputs a read instructionsignal to the first CPU 160. The confirm button 1402 is a button forreceiving a confirmation operation by a user and a request of displayingthe status of dirt at the imaging position. When the confirm button 1402is pressed, the display operation device 106 receives a confirmationoperation by a user, transmits a confirmation accept signal thatindicates that the confirmation operation has been received, to thenotifying module 165, and displays a status display screen that displaysthe status of dirt at the imaging position. The set button 1403 is abutton for instructing display of a setting screen (not shown) forperforming a variety of settings on the image reading apparatus 100.Note that, when the notifying module 165 detects dirt, a warning image1404 indicating the presence of dirt is displayed near the confirmbutton 1402. The warning image 1404 is an example of an image forproviding the warning.

FIGS. 14B, 14C are schematic views depicting examples of status displayscreens displayed on the display operation device 106. FIG. 14B is anexample of a status display image 1410 when a warning is notified to auser and also an example of an image for providing the warning. FIG. 14Cis an example of a status display screen 1420 when a warning is notnotified to a user.

As depicted in FIG. 14B, the status display screen 1410 displays acharacter 1411 that indicates the presence of dirt and prompts cleaning,an image 1412 that indicates the position of dirt, and an end button1413.

The image 1412 indicates: whether the dirt is on the transparent memberon the side of the imaging sensor that capture a white reference imageor on the transparent member on the side of the white reference memberthat is captured in the white reference image; the dirt position on thetransparent member; and if the dirt is severe, moderate, or minor. Inthe image 1412, when there is dirt on the transparent member, theposition of dirt on the transparent member is indicated distinctly frompositions without dirt. For example, to identify a dirt degree by thedensity of color, a position corresponding to severe dirt is displayedin black, a position corresponding to moderate dirt is displayed ingray, a position corresponding to minor dirt is displayed in lightergray, and a position without dirt is displayed in white. Alternatively,to identify dirt degree by color, a position corresponding to severedirt may be displayed in red, a position corresponding to moderate dirtmay be displayed in yellow, a position corresponding to minor dirt maybe displayed in blue, and a position without dirt may be displayed inwhite.

The notifying module 165 generates and provides, on the status displayscreen 1410, the warning, and a notification of the imaging positions ofpixels corresponding to severe, moderate, or minor dirt, i.e., pixels ofwhich dirt degree is equal to or more than the first, third, or secondthreshold, to a user. In this way, a user can accurately recognize theposition of a dirt substance causing dirt and clean the position.

When the end button 1413 is pressed, the display operation device 106displays the reception screen 1400 again.

Whereas, the status display screen 1420 depicted in FIG. 14C displays acharacter 1421 that indicates there is no dirt, an image 1422, and anend button 1423.

In this way, the notifying module 165 generates and provides the warningto a user according to the dirt degree at the imaging position in thewhite reference image. The notifying module 165 generates and providesthe warning when there is severe dirt at the imaging position, or doesnot generate and provide the warning when there is no dirt at theimaging position. Whereas, when there is moderate dirt at the imagingposition, the notifying module 165 generates and provides the warningonly when the scan count exceeds the scan count threshold. Further, whenthere is minor dirt at the imaging position and the dirt has not beendetected as moderate or severe dirt previously, the notifying module 165does not generate and provide the warning regardless of whether the scancount exceeds the scan count threshold or not. Whereas, when there isminor dirt at the imaging position and the dirt has been detected asmoderate or severe dirt previously, the notifying module 165 generatesand provides the warning only when the scan count exceeds the scan countthreshold as in a case where there is moderate dirt.

In this way, the notifying module 165 can generate and provide thewarning at appropriate timing according to a dirt degree at the imagingposition. In particular, when there is severe dirt, the notifying module165 generates and provides the warning until a user confirms the dirt.Thus, the user can recognize the presence of dirt at the imagingposition and clean it before scanning a document. This decreasessituations where noise line is generated in the document image andre-scanning of the document is required, whereby the image readingapparatus 100 can improve user convenience. Whereas, when there ismoderate dirt, the image reading apparatus 100 generates and provides awarning at a certain cycle, thereby preventing troubling a user, whilemaking the user moderately recognize the presence of dirt.

The first dirt substance detection processing module 162 performs thefirst processing using a dirt substance detection result from the seconddirt substance detection processing module 242. As such, the first dirtsubstance detection processing module 162 can better detect a dirtsubstance.

Note that, at step S216, when a user has already confirmed dirt, thenotifying module 165 may not go without generating and providing thewarning yet may change the timing of generating and providing thewarning. In such a case, for example, the notifying module 165 generatesand provides the warning at every predetermined count even when a userhas already confirmed the dirt.

Alternatively, the first dirt substance detection processing module 162may detect dirt based on other reference images than the white referenceimage in the first processing. In this case, the first image acquiringmodule 161 turns on the light source 124 and causes the imaging sensor125 to capture an image of the white reference member 126 to generate awhite reference image, as well as, turns off the light source 124 andcauses the imaging sensor 125 to capture an image of the white referencemember 126 to generate a black reference image. The first imageacquiring module 161 generates a reference image having, as a pixelvalue of each pixel, a value obtained by subtracting the pixel value ofa pixel in the black reference image from the pixel value of acorresponding pixel in the white reference image.

FIG. 15 is a flowchart depicting an example of the operation ofconfirmation processing. The confirmation processing depicted in FIG. 15is carried out at step S106 of the flowchart depicted in FIG. 11.

First, the notifying module 165 determines whether a warning has beennotified to a user (step S301). When no warning has been notified, thenotifying module 165 does not perform particular processing and ends theset of steps.

Whereas, when the warning has been generated and provided, i.e., aftergenerating and providing the warning, the notifying module 165determines whether the display operation device 106 has received aconfirmation operation by a user based on whether a confirmationacceptance signal has been received from the display operation device106 (step S302).

When the display operation device 106 has received a confirmationoperation by a user, the notifying module 165 stores the confirmationoperation information that indicates that the confirmation operation hasbeen received, in the first storage device 140, in association with thedirt position displayed on the image 1412 of the status display screen1410 (step S303). Note that the notifying module 165 thereafterperiodically monitors the confirmation operation information, and whendirt is not detected at a position associated with the confirmationoperation information, the notifying module 165 deletes the confirmationoperation information from the first storage device 140.

Next, the notifying module 165 initializes (resets) the scan countstored in the first storage device 140 to zero (step S304). In this way,as the scan count becomes equal to or less than the scan countthreshold, the notifying module 165 does not generate and provide thewarning to a user even when moderate dirt on which the warning hasalready been notified to a user is redetected. Thus, the notifyingmodule 165 keeps generating and providing the warning to a user who hasnot confirmed the warning, and prevents repeating providing the samewarning to a user who has confirmed the warning, thereby preventingtroubling the user.

Next, the notifying module 165 changes the scan count thresholdaccording to the confirmation time from providing the warning until thedisplay operation device 106 receives a confirmation operation by a user(step S305). For example, the notifying module 165 changes the scancount threshold larger as the confirmation time is longer. In this way,when a user does not care about the dirt, the notifying module 165 canprevent troubling the user by reducing the frequency of providing thewarning.

Next, the information acquiring module 168 determines whether or not thecover of the image reading apparatus 100 has been opened and closedbased on an open/close signal, which indicates whether the upper housing102 is open or closed with respect to the lower housing 101, output fromthe open/close sensor 114 (step S306). When the state of the upperhousing 102 has changed from a closed state to an open state withrespect to the lower housing 101, then, further changed to a closedstate, the information acquiring module 168 determines that the cover ofthe image reading apparatus 100 has been opened and closed. In such acase, the information acquiring module 168 acquires open/closeinformation that indicates that the cover of the image reading apparatus100 has been opened and closed. Note that the open/close sensor 114 maydetermine whether or not the cover of the image reading apparatus 100has been opened and closed and the information acquiring module 168 mayacquire the open/close information from the open/close sensor 114.

When the information acquiring module 168 has acquired the open/closeinformation, the first CPU 160 re-executes the overall processingdepicted in FIG. 11 from step S101. In such a case, the first imageacquiring module 161 acquires newly captured a white reference image,the dirt degree calculation module 164 newly calculates a dirt degreebased on the newly captured white reference image, and the notifyingmodule 165 generates and provides the warning to a user according to thenewly calculated dirt degree. As such, as the notifying module 165automatically determines whether there is remaining dirt after the imageposition was cleaned and generates and provides the warning to a user ifthere is remaining dirt, the user can immediately recognize that thereis remaining dirt.

Whereas, when the information acquiring module 168 has not acquiredopen/close information, the notifying module 165 determines whether acertain time period (for example, one minute) has passed after providingthe warning (step S307). When a certain time period has not passed afterproviding the warning, the notifying module 165 does not performparticular processing and ends the set of steps.

When a certain time period has passed after providing the warning, i.e.,when the information acquiring module 168 has not acquired open/closeinformation within the certain time period after providing the warning,the notifying module 165 changes the scan count threshold (step S308)and ends the set of steps. For example, the notifying module 165increases the scan count threshold. Note that when the informationacquiring module 168 has not acquired open/close information even thoughthe display operation device 106 had received a confirmation operationby a user, the notifying module 165 may further increase the scan countthreshold. Further, the notifying module 165 may change the scan countthreshold so that the scan count threshold becomes larger as the timeperiod from providing the warning to acquisition of open/closeinformation is longer. In this way, when a user does not care about thedirt, the notifying module 165 can prevent troubling the user byreducing the frequency of providing the warning.

Note that, even when a warning has been notified to a user in the secondprocessing instead of the first processing, the information acquiringmodule 168 may determine whether or not the cover of the image readingapparatus 100 has been opened and closed, and, when the cover has beenopened and closed, the first CPU 160 may re-execute the overallprocessing as depicted in FIG. 11. In this way, even when a warning wasnotified to a user on the side of the information processing apparatus200 and a user cleaned the dirt, the image reading apparatus 100 canautomatically determine whether there is remaining dirt and, if there isremaining dirt, generate and provide the warning to a user.

Note that each processing of steps S304, S305, S306, S307 to S308 may beomitted.

FIG. 16 is a flowchart depicting an example of the operation ofthreshold setting processing of the image reading apparatus 100. Thefollowing will describe an example of the operation of the thresholdsetting processing of the image reading apparatus 100 with reference tothe flowchart depicted in FIG. 16. The operation flow as will bedescribed below is performed primarily by the first CPU 160 jointly witheach component of the image reading apparatus 100 according to a programprestored in the first storage device 140. This operation flow isperformed immediately after start-up of the device.

First, the setting module 166 sets a first threshold, a secondthreshold, and a third threshold at predefined values (step S401). Thesetting module 166 sets the first threshold based on a binarizationthreshold for binarizing a correction image to detect characters fromthe correction image in the optical character recognition (OCR)processing performed by the information processing apparatus 200. Thesetting module 166, for example, sets the first threshold as a valueobtained by subtracting the binarization threshold (or plus or minus apredetermined margin value) from the gradient value representing white(for example, 255). In this way, the image reading apparatus 100 candetect dirt that has density that can be recognized as a part of blackcharacters in contrast to a white background in the characterrecognition processing as severe dirt and immediately a user of awarning.

Whereas, the setting module 166 sets the third threshold as a value thatcan distinguish visually recognizable dirt for human eyes from visuallyunrecognizable dirt in a multi-level image. In prior evaluation, thesetting module 166 accepts, from an administrator, gradient valuescorresponding to visually recognizable dirt and gradient valuescorresponding to visually unrecognizable dirt in a white reference image(multi-level image) captured dirt of a variety of densities. The settingmodule 166 calculates an average value of gradient values correspondingto visually recognizable dirt and gradient values corresponding tovisually unrecognizable dirt, and sets the third threshold as a valueobtained by subtracting the average value (or plus or minus apredetermined margin value) from a gradient value representing white. Inthis way, the image reading apparatus 100 can detect visuallyrecognizable dirt in a multi-level image as moderate dirt and generateand provide the warning at a certain cycle.

Further, the setting module 166 sets the second threshold as a valueobtained by subtracting an allowable error value that is set in theimage reading apparatus 100 with regard to the reading value of theimaging sensor 125 from the third threshold. In this way, the imagereading apparatus 100 can prevent failing to detect visuallyrecognizable dirt as moderate dirt due to the precision error of theimage reading apparatus 100.

Next, the setting module 166 determines whether the threshold acquiringmodule 167 has newly acquired a binarization threshold from theinformation processing apparatus 200 via the first interface device 135(step S402). When the threshold acquiring module 167 has newly acquireda binarization threshold, the setting module 166 resets the firstthreshold based on the newly acquired binarization threshold (stepS403).

Next, the setting module 166 determines whether the first resultacquiring module 163 has newly acquired a second result from theinformation processing apparatus 200 via the first interface device 135(step S404). When the first result acquiring module 163 has newlyacquired a second result, the setting module 166 changes the firstthreshold, the second threshold, or the third threshold based on thenewly acquired second result (step S405), and returns the processing tostep S402. The setting module 166 changes the first threshold, thesecond threshold or the third threshold to a smaller value than thepresent value, for example, when a dirt substance causing noise line isdetected in the second processing, and changes the first threshold, thesecond threshold or the third threshold to a larger value than thepresent value, when a dirt substance is not detected in the secondprocessing. In this way, the image reading apparatus 100 can moreaccurately generate and provide the warning when there is dirt that cancause noise line in the correction image.

Note that each processing of steps S402 to S403, S404 to S405 may beomitted.

FIG. 17 is a flowchart depicting an example of the operation of theoverall processing of an information processing apparatus 200. Thefollowing will illustrate an example of the operation of the overallprocessing of the information processing apparatus 200 with reference tothe flowchart depicted in FIG. 17. Note that the operation flow as willbe described below is performed primarily by the second CPU 240 jointlywith each component of the information processing apparatus 200according to a program prestored in the second storage device 220. Thisoperation flow is periodically performed.

First, the second image acquiring module 241 acquires a correction imagefrom the image reading apparatus 100 via the second interface device203. Further, the second result acquiring module 243 acquires a firstresult from the image reading apparatus 100 via the second interfacedevice 203. The second result acquiring module 243 acquires a secondresult relating to the previously conveyed document from the noise linedetecting module 249. The device information acquiring module 244acquires device information from the image reading apparatus 100 via thesecond interface device 203 (step S501). Note that the second resultacquiring module 243 may acquire the first result only when a new firstresult is transmitted from the image reading apparatus 100. Further, thedevice information acquiring module 244 may omit acquisition of thedevice information when the device information has already beenacquired.

Next, the second dirt substance detection processing module 242 executesthe second processing (step S502) and ends the set of steps. The seconddirt substance detection processing module 242 detects a dirt substancefrom the correction image in the second processing. The details of thesecond processing will be described later.

FIG. 18 is a flowchart depicting an example of the operation of thesecond processing. The second processing depicted in FIG. 18 is carriedout at step S502 of the flowchart depicted in FIG. 17.

First, the edge pixel extracting module 245 extracts first edge pixelsin horizontal and vertical directions from the correction image (stepS601). The edge pixel extracting module 245 generates a first edge imageconstituted by the first edge pixels in horizontal and verticaldirections of the correction image.

The edge pixel extracting module 245 calculates the absolute value of adifference of gradient values between both side pixels of a pixel ofinterest in a horizontal direction in the correction image or theabsolute value of a difference of gradient values of pixels that areapart by a predetermined distance from the pixel of interest(hereinafter, referred to as a peripheral difference value) and, whenthe peripheral difference value exceeds a fourth threshold, the edgepixel extracting module 245 extracts the pixel of interest as a firstvertical edge pixel. This peripheral difference value indicates theintensity of the edge in the edge pixels. The fourth threshold may beset, for example, at a difference of gradient values in an image thatcan be visually distinguished by human eyes (for example, 20). The edgepixel extracting module 245 performs the same processing in a verticaldirection and extracts first horizontal edge pixels. Then, the edgepixel extracting module 245 generates a first horizontal edge image anda first vertical edge image for a horizontal direction and a verticaldirection respectively.

Note that the edge pixel extracting module 245 may instead calculate, asa peripheral difference value, the absolute value of a differencebetween a gradient value of the pixel of interest in the correctionimage and the average value of gradient values of peripheral pixelslocated both sides of the pixel of interest or located within apredetermined range from the pixel of interest in a horizontal orvertical direction. Alternatively, the edge pixel extracting module 245may extract the first edge pixel by comparing the gradient value of eachpixel with a threshold. For example, when the gradient value of thepixel of interest is less than a threshold and the gradient values ofpixels on both sides of the pixel of interest or pixels that are apartfrom the pixel of interest by a predetermined distance in a horizontalor vertical direction are equal to or more than the threshold, the edgepixel extracting module 245 determines the pixel of interest as thefirst edge pixel.

FIG. 19A is a schematic view depicting an example of a correction image1900.

In the correction image 1900 depicted in FIG. 19A, a document 1901 andthe periphery thereof, as well as, a shadow 1903 formed on the whitereference member 126 by the leading end 1902 of the document 1901 arecaptured. In the correction image 1900, pixels corresponding to the ends1904 to 1907 of the document 1901 are extracted as the first edgepixels.

Next, the document region detecting module 246 detects a document regionbased on the first edge pixels (step S602).

The document region detecting module 246 first extracts a plurality ofstraight lines from the first edge pixels extracted by the edge pixelextracting module 245. The document region detecting module 246 extractsstraight lines from the first horizontal edge image and the firstvertical edge image. The document region detecting module 246 extractsstraight lines using Hough transform. Note that the document regiondetecting module 246 may extract straight lines using a least squaresmethod. Alternatively, the document region detecting module 246 maygroup the first edge pixels adjacent to one another into one by labelingthem and extract straight lines by connecting the first edge pixels atboth ends in a horizontal or vertical direction from among the firstedge pixels included in each group.

Next, the document region detecting module 246 detects a rectangle fromthe extracted plurality of straight lines. The document region detectingmodule 246 extracts a plurality of rectangle candidates, eachconstituted by four straight lines where each two of the extractedplurality of straight lines are substantially perpendicular to eachother. The document region detecting module 246 first selects onestraight line in a horizontal direction (hereinafter, referred to as thefirst horizontal line) and extracts another straight line in ahorizontal direction that is substantially parallel (for example, ±3° orless) to the selected straight line and apart from the selected straightline by threshold Th1 or more (hereinafter, referred to as the secondhorizontal line). Next, the document region detecting module 246extracts a straight line in a vertical direction substantiallyperpendicular to the first horizontal line (for example, ±3° or lesswith respect to 90°) (hereinafter, referred to as the first verticalline). Next, the document region detecting module 246 extracts astraight line in a vertical direction that is substantiallyperpendicular to the first horizontal line and apart from the firstvertical line by a threshold Th2 or more (hereinafter, referred to asthe second vertical line). Note that the thresholds Th1 and Th2 may bepredefined according to the size of a document to be read by the imagereading apparatus 100 and may be the same values.

The document region detecting module 246 extracts all combinations of afirst horizontal line, a second horizontal line, a first vertical line,and a second vertical line that satisfy the above conditions from amongall the extracted straight lines and extracts rectangles constituted bythe extracted combinations as rectangle candidates. The document regiondetecting module 246 calculates the areas of the extracted rectanglecandidates and eliminates the rectangle candidates of which area is lessthan a predetermined value. The document region detecting module 246detects a rectangle candidate with the largest area from the remainingrectangle candidates as a document region. Whereas, when there is noremaining rectangle candidate, the document region detecting module 246detects no document region.

In the correction image 1900 depicted in FIG. 19A, straight linescorresponding to the ends 1904 to 1907 of the document 1901 areextracted and the document region 1908 surrounded by the straight linesis extracted.

Next, the shadow region detecting module 247 determines a predeterminedrange for detecting a shadow region in a correction image based on thedevice information acquired by the device information acquiring module244 (step S603). The shadow region is a region that captures a shadowformed on the white reference member 126 by the leading end or rear endof the document in the correction image and the predetermined range isdetermined by an adjacent region outside of the document region detectedin the correction image. For example, when the device informationindicates that the first light source 124 a is provided on the upstreamside of the first imaging sensor 125 a in the document conveyancedirection A3, as depicted in FIG. 7, a shadow is formed by the leadingend of the document on the second white reference member 126 b. In sucha case, the shadow region detecting module 247 determines a range withina predetermined distance from the upper end of the document regioncorresponding to the leading end of the document (for example, adistance equivalent to 5 mm) as a predetermined range in a firstcorrection image. Likewise, when the device information indicates thatthe second light source 124 b is provided on the downstream side of thesecond imaging sensor 125 b in the document conveyance direction A3, ashadow is formed by the rear end of the document on the first whitereference member 126 a. In such a case, the shadow region detectingmodule 247 determines a range within a predetermined distance from thelower end of the document region corresponding to the rear end of thedocument as a predetermined range in a second correction image.

In the correction image 1900 depicted in FIG. 19A, a range 1910 within apredetermined distance, in an outward direction of the document region1908, from the upper end 1904 of the document region 1908 is determinedas a predetermined range.

Next, the shadow region detecting module 247 extracts second edge pixelswithin the determined predetermined range and extracts a plurality ofstraight lines based on the extracted second edge pixels (step S604).

The shadow region detecting module 247 extracts the second edge pixelsin the same way in which the edge pixel extracting module 245 extractsthe first edge pixels. However, the shadow region detecting module 247extracts a plurality of levels of second edge pixels with differentdegrees of peripheral difference values (edge intensities). The shadowregion detecting module 247 first sets an initial value at a fifththreshold and extracts the second edge pixels of which peripheraldifference value exceeds the fifth threshold. The initial value is set,for example, at the same or a smaller value than the fourth threshold.Next, the shadow region detecting module 247 extracts straight linesfrom the extracted second edge pixels in the same way in which thedocument region detecting module 246 extracts straight lines, andextracts line segments of a region corresponding to the extracted secondedge pixels in a horizontal direction from among the extracted straightlines.

Next, the shadow region detecting module 247 changes the fifth thresholdto a smaller value than the present value, extracts the second edgepixels of which peripheral difference value exceeds the changed fifththreshold from a range where line segments have not extracted in ahorizontal direction, and extracts new line segments from among theextracted second edge pixels. The shadow region detecting module 247extracts a plurality of levels of second edge pixels with differentdegrees of peripheral difference values while changing the fifththreshold to smaller values until line segments are extracted from theentire range in a horizontal direction and extracts a line segment fromthe second edge pixels at each level.

FIG. 19B is a schematic view for illustrating a plurality of linesegments extracted based on the second edge pixels. FIG. 19B is anenlarged view of the predetermined range 1910 depicted in FIG. 19A.

As depicted in FIG. 19B, when an end of the document 1901 is curved, theshadow region 1911 does not become a rectangular region. In the exampledepicted in FIG. 19B, first, the second edge pixels 1921 of a firstlevel are extracted and a line segment 1922 is extracted from the secondedge pixels 1921. Next, the second edge pixels 1923 of a second levelthat is lower than the first level are extracted and a line segment 1924is extracted from the second edge pixels 1923. Then, the second edgepixels 1925 of a third level that is lower than the second level areextracted and a line segment 1926 is extracted from the second edgepixels 1925.

Next, the shadow region detecting module 247 detects a region in asecond predetermined range (for example, a distance equivalent to 1 mm)from each of a plurality of extracted line segments as a shadow region(step S605). The shadow region detecting module 247 detects a shadowregion obtained by connecting regions within the second predeterminedrange in a vertical direction from the line segments.

In the example depicted in FIG. 19B, a shadow region is detected as aregion 1930 obtained by connecting a region 1927 within the secondpredetermined range from the line segment 1922, a region 1928 within thesecond predetermined range from the line segment 1924, and a region 1929within the second predetermined range in a vertical direction from theline segment 1926. In this way, even when an end of the document 1901 iscurved, the shadow region detecting module 247 can accurately detect ashadow region by detecting a shadow region using a plurality of linesegments.

Next, the noise pixel extracting module 248 specifies a priority rangefor preferentially detecting a dirt substance in the shadow region usinga position within a white reference image where a dirt substance isdetected, i.e., a position of the dirt substance detected by the firstdirt substance detection processing module 162 as indicated in the firstresult (step S606).

To reduce a load of noise pixel determination processing, the noisepixel extracting module 248 sets pixels apart from one another by afirst distance in a horizontal direction as target pixels fordetermining whether the pixels are noise pixels or not, instead ofdetermining whether they are noise pixels or not for all pixels in theshadow region. Whereas, the noise pixel extracting module 248 sets arange within a predetermined distance from a position corresponding tothe position where a dirt substance is detected in the white referenceimage as a priority range in the shadow region. As for pixels in thepriority range, the noise pixel extracting module 248 sets pixelsadjacent to one another in a horizontal direction or pixels apart fromone another by a second distance that is shorter than the first distanceas target pixels.

FIG. 20A is a schematic view for illustrating a priority range. FIG. 20Ais an enlarged view of the shadow region 1930 depicted in FIG. 19B.

In the example depicted in FIG. 20A, pixels spaced apart from oneanother by a first distance (4 pixels) in a horizontal direction are setas target pixels 2001. Further, a dirt substance is detected at aposition in a white reference image corresponding to a position 2002 inthe shadow region 1930, and a range within a predetermined distance (4pixels) from the position 2002 is set as a priority range 2003. In thepriority range 2003, pixels spaced apart from one another by a seconddistance (2 pixels) are set as the target pixels 2004. In this way, thenoise pixel extracting module 248 can efficiently extract noise pixelssince the noise pixel extracting module 248 can selectively scan aregion where a dirt substance is likely to exist while reducing the loadof noise pixel determination processing.

Further, the noise pixel extracting module 248 specifies a priorityrange for preferentially detecting a dirt substance in a shadow regionusing a position within a correction image where a dirt substance hasbeen previously detected, indicated by a previous second result by thesecond dirt substance detection processing module 242. The noise pixelextracting module 248 specifies the priority range in the same way asthe case where a priority range is specified using a position of a dirtsubstance detected by the first dirt substance detection processingmodule 162.

Next, the noise pixel extracting module 248 extracts noise pixels in theshadow region based on the specified priority range (step S607). In thisway, the noise pixel extracting module 248 specifies a priority rangebefore executing the second processing. The noise pixel extractingmodule 248 extracts, as a noise pixel, a pixel where a differencebetween the gradient value of the shadow region and the gradient valueof the noise pixel is equal to or more than a sixth threshold.

As depicted in FIG. 19A, the shadow region has gradation along avertical direction; the shadow region is the darkest (lower luminance)around the upper end of the document and gradually becomes brighter(higher luminance) as it goes upward. The noise pixel extracting module248 calculates an average value of the gradient values of pixels foreach horizontal line in the shadow region, and extracts, as a noisepixel, a pixel where the absolute value of a difference between thegradient value of the pixel of interest and the average value calculatedfor a horizontal line to which the pixel of interest belongs is equal toor more than the sixth threshold. As described above, as the shadowformed on the white reference member 126 is gray that is an intermediatecolor between white and black, not only a black dirt substance but alsoa white dirt substance is extracted as noise pixels from the shadowregion in the white reference image.

FIG. 20B is a graph for illustrating noise pixels.

The horizontal axis of FIG. 20B indicates a gradient value and thevertical axis indicates a position in a vertical direction in acorrection image. The straight line 2010 of FIG. 20B indicates anaverage value of the gradient values of pixels for each horizontal linein the shadow region. As described above, the straight line 2010 isinclined as the shadow region has gradation along the verticaldirection. The pixels 2013, 2014 plotted within a range 2012 where adistance 2011 in a horizontal axis direction from this straight line2010 is equal to or less than the sixth threshold are not extracted asnoise pixels, rather, pixels 2015, 2016 plotted outside the range 2012are extracted as noise pixels.

Next, the noise line detecting module 249 detects noise pixels, thenumber of which connected with one another is equal to or more than apredetermined number (for example, 4 pixels), from noise pixelsextracted by the noise pixel extracting module 248 as a noise line (stepS608). The noise line detecting module 249 determines whether to connectnoise pixels extracted by the noise pixel extracting module 248 in avertical direction (whether adjacent noise pixels exist). The noise linedetecting module 249 groups mutually connected noise pixels into oneand, when the length of each group in a vertical direction is equal toor more than a predetermined value (for example, a distance equivalentto 0.5 mm), detects the group as a noise line. In this way, the noiseline detecting module 249 detects a dirt substance causing a noise linebased on a difference between the gradient value of a shadow region andthe gradient value of the dirt substance. By detecting a noise line froma shadow region outside of a document region, the noise line detectingmodule 249 can accurately detect a noise line without being affected bythe content, such as ruled lines, in the document.

Next, the noise line detecting module 249 determines whether a noiseline is detected from the correction image (step S609). When no noiseline is detected, the noise line detecting module 249 transfers theprocessing to step S616.

Whereas, when a noise line is detected, the noise line detecting module249 stores a position in a horizontal direction where the noise line isdetected in the correction image as a noise line position in the secondstorage device 220 (step S610).

Next, the noise line detecting module 249 determines whether a user hasconfirmed the noise line (step S611). When the operation device 202 hasreceived a confirmation operation by a user after a warning on the noiseline had previously been notified to a user, the noise line detectingmodule 249 determines that the user has confirmed the noise line. Whenthe first result indicates that dirt is detected and the dirt positionof the detected dirt corresponds to the noise line position of thepresent noise line, and the detected dirt has been confirmed by a user,the noise line detecting module 249 may also determine that the user hasalready confirmed the noise line.

When a user has already confirmed the noise line, the noise linedetecting module 249 transfers the processing to step S615. As such,when a user has already confirmed a dirt substance in the image readingapparatus 100, the noise line detecting module 249 does not generate andprovide the warning.

Whereas, when a user has not confirmed the noise line, the noise linedetecting module 249 generates and provides the warning to a user (stepS612). The noise line detecting module 249 generates and provides thewarning to a user by displaying the similar image as the receptionscreen depicted in FIG. 14A and the status display screen depicted inFIGS. 14B and 14C on the display device 201.

In this way, the noise line detecting module 249 keeps generating andproviding the warning to a user who has not confirmed the warning andprevents repeating providing the same warning to a user who hasconfirmed the warning, thereby preventing troubling the user.

Next, the noise line detecting module 249 determines whether the displaydevice 201 has received a confirmation operation by a user based onwhether the operation device 202 has received a confirmation acceptancesignal (step S613).

When the operation device 202 has received a confirmation operation froma user, the noise line detecting module 249 stores the confirmationoperation information that indicates that the confirmation operation hasbeen received, in the second storage device 220, in association with thenoise line position of the noise line (step S614). Note that the noiseline detecting module 249 thereafter periodically monitors theconfirmation operation information, and, when the noise line is notdetected at a position associated with the confirmation operationinformation, the noise line detecting module 249 deletes theconfirmation operation information from the second storage device 220.

Next, the noise line detecting module 249, the determination module 250,and the correction module 251 perform correction processing (step S615).In the correction processing, the correction module 251 corrects thedocument region of the correction image based on the noise linedetection result by the noise line detecting module 249. The details ofthe correction processing will be described later.

Next, the noise line detecting module 249 stores the second result inthe second storage device 220, as well as, transmits the second resultto the image reading apparatus 100 via the second interface device 203(step S616).

Next, the correction module 251 stores the correction image in thesecond storage device 220, as well as, displays the correction image onthe display device 201 (step S617), and ends the set of steps.

As such, the second dirt substance detection processing module 242executes the second processing using the dirt substance detection resultby the first dirt substance detection processing module 162 to detect adirt substance from the correction image. As such, the second dirtsubstance detection processing module 242 can better detect a dirtsubstance.

Note that, at step S611, when a user has already confirmed the noiseline, the noise line detecting module 249 may not go without generatingand providing the warning yet may change the timing of generating andproviding the warning. In such a case, for example, the noise linedetecting module 249 generates and provides the warning at everypredetermined count even when a user has already confirmed the noiseline.

FIG. 21 is a flowchart depicting an example of the operation of thecorrection processing. The correction processing depicted in FIG. 21 iscarried out at step S615 of the flowchart depicted in FIG. 18.

First, the noise line detecting module 249 specifies the noise linerange, corresponding to a noise line detected in the shadow region, inthe document region detected by the document region detecting module 246(step S701).

As depicted in FIG. 19A, when there are noise lines 1912 to 1914 in theshadow region, the noise lines are likely to extend in a verticaldirection and present in the document region 1908. Thus, the noise linedetecting module 249 estimates that a noise line is present in thedocument region at a horizontal position corresponding to the noise lineposition of the noise line detected in the shadow region, and specifiesthe horizontal position in the document region corresponding to thenoise line position of the noise line detected in the shadow region as anoise line region.

The noise line detecting module 249 further determines whether or not anoise line is present in the identified noise line region. In the sameway as the edge pixel extracting module 245, the noise line detectingmodule 249 extracts third edge pixels in the noise line region, anddetermines that there are noise lines in the specified noise lineregion, i.e., in the document region, when the number or ratio of theextracted third edge pixels is equal to or more than a predeterminednumber or ratio. The noise line detecting module 249 includes thedetermination result in the second result. This determination result isused by the notifying module 165 to determine whether a dirt substanceis on the side of the imaging sensor or on the side of the whitereference member.

Next, the determination module 250 determines whether the noise line inthe document region overlaps the content based on a difference betweenthe gradient value of the noise line region identified by the noise linedetecting module 249 and the gradient values of the peripheral pixels inthe noise line region (step S702). The peripheral pixels may be, forexample, pixels located within a predetermined range (for example, 20pixels) from the noise line region.

FIG. 22 is a graph for illustrating a relationship between a noise lineand a background of a document.

The horizontal axis of FIG. 22 indicates the gradient value of thebackground of a document and the vertical axis indicates the gradientvalue of noise lines. Each dot 2201 of FIG. 22 corresponds to eachdocument image of a document of a different single color such that anoise line is generated in the document image, and is plotted at acoordinate corresponding to the gradient value of the background of thedocument and the gradient value of the noise line in each documentimage. A noise line occurs when light from the light source 124 isreflected against a dirt substance, such as paper dust, adhered to thetransparent member 127 between the imaging sensor 125 and the document.As such, as depicted in FIG. 22, when a noise line overlaps thebackground of a document in the document image, the gradient value ofthe noise line pixels corresponding to the noise line becomes slightlyhigher than the gradient value of the background pixels capturing thebackground of the document around the noise line. Further, as thebackground is darker, the influence of reflection, against thebackground, of the light from the light source 124 becomes larger,while, as the background is brighter, the influence of reflection,against the background, of the light from the light source 124 becomessmaller. As such, as the gradient value of the background pixel islower, the difference between the gradient value of the noise linepixels and the gradient value of the background pixels becomes larger;as the gradient value of the background pixel is higher, the differencebetween the gradient value of the noise line pixels and the gradientvalue of the background pixels becomes smaller.

As the result of measurement using a variety of documents, it is foundthat the relationship of the following formulas (1) and (2) can beestablished between the gradient value of pixels corresponding to anoise line and the gradient value of peripheral background pixels:(Gradient value of noise line pixels)>(Gradient values of backgroundpixels)  (1)(Gradient value of noise line pixels)<0.8×(Gradient values of backgroundpixels)+80  (2)

Thus, when the gradient value of a noise line region and the averagevalue of the gradient values of peripheral pixels of the noise lineregion satisfy the relationship of the following formulas (3) and (4),the determination module 250 determines that the noise line regionoverlaps the background yet does not overlap the content. Whereas, whenthe gradient value of the noise line region and the average value of thegradient values of peripheral pixels of the noise line region do notsatisfy the relationship of the following formulas (3) and (4), thedetermination module 250 determines that the noise line region does notoverlap the content.(Gradient value of noise line pixels)>(Average value of gradient valuesof peripheral pixels)   (3)(Gradient value of noise line pixels)<α×(Average value of gradientvalues of peripheral pixels)+β  (4)where α is a value larger than 0.6 and smaller than 1.0, and preferably0.8; β is a value larger than 0 and smaller than 160, and preferably 80.

FIGS. 23A to 23C are graphs for illustrating a relationship between anoise line region and a content. The horizontal axis of FIGS. 23A to 23Cindicates the horizontal position in a correction image and the verticalaxis indicates the gradient value.

FIG. 23A depicts the gradient value of a horizontal line in a correctionimage with a noise line overlapping a background. In this correctionimage, a noise line is in a region 2301 and a background is inperipheral regions 2302, 2303. In the example depicted in FIG. 23A, thegradient value 2304 of the noise line region 2301 is larger than theaverage value 2305 of the gradient values of the peripheral regions2302, 2303 and a difference therebetween is sufficiently small, thus,formulas (3) and (4) are satisfied and the noise line region isdetermined not to overlap the content.

FIG. 23B depicts the gradient value of a horizontal line in a correctionimage with a noise line overlapping a content that has a higher gradientvalue than the background. In this correction image, a noise line is ina region 2311, a content with a higher gradient value is in peripheralregions 2312, 2313, and a background is in further peripheral regions2314, 2315. The content regions 2312, 2313 have sufficiently highergradient values compared with the background regions 2314, 2315 so thata user can easily identify the content. Thus, the noise line region 2311is buried in the content regions 2312, 2313, and the gradient value 2316of the noise line region 2311 becomes a substantially similar level asthe gradient values of the content regions 2312, 2313. Whereas, as theperipheral regions 2312 to 2315 include the background in addition tothe content, the average value 2317 of the gradient values of theperipheral regions 2312 to 2315 becomes a value close to the gradientvalue of the background. Thus, a difference between the gradient value2316 of the noise line region 2311 and the average value 2317 of thegradient values of the peripheral regions 2312 to 2315 becomes large,and the formula (4) is not satisfied, whereby the noise line region isdetermined to overlap the content.

FIG. 23C depicts the gradient value of a horizontal line in a correctionimage with a noise line overlapping a content that has a lower gradientvalue than the background. In this correction image, a noise line is ina region 2321 and a content with a lower gradient value is in peripheralregions 2322, 2323, and a background is in further peripheral regions2324, 2325. The content regions 2322, 2323 have sufficiently lowgradient values compared with the background regions 2324, 2325 so thata user can easily identify the content. Thus, the gradient value 2326 ofthe noise line region 2321 becomes a higher value than the gradientvalues of the content regions 2322, 2323, but is a sufficiently lowervalue than the gradient values of the background regions 2324, 2325. Asthe peripheral regions 2322 to 2325 include the background in additionto the content, the average value 2327 of the gradient values of theperipheral regions 2322 to 2325 becomes a value close to the gradientvalue of the background. Thus, the gradient value 2326 of the noise lineregion 2321 becomes smaller than the average value 2327 of the gradientvalues of the peripheral regions 2322 to 2325, and the formula (3) isnot satisfied, whereby the noise line region is determined to overlapthe content.

When the determination module 250 determines that the noise line regiondoes not overlap the content, the correction module 251 corrects thevertical region based on the peripheral pixels of the noise line region(step S703) and ends the set of steps. The correction module 251 uses,for example, a known linear interpolation technique to correct the noiseline region using the gradient values of the peripheral pixels of thenoise line region. In this way, when the periphery of the noise lineregion is a monotonous background, the correction module 251 can burythe noise line region in the background.

Whereas, when the noise line region is determined to overlap thecontent, the determination module 250 determines whether the content isa character or not (step S704). The determination module 250 detects acharacter from the correction image, for example, using a knowncharacter recognition (OCR) technique. The determination module 250calculates the likelihood (coincidence) of including each preregisteredcharacter in each region in the correction image and, when thelikelihood of the character with the highest likelihood is equal to ormore than a predetermined threshold, the determination module 250determines that the region includes the character. When a character isdetected, the determination module 250 determines whether theoverlapping region that is determined to overlap the content in thenoise line region overlaps a character region where the character isdetected. When the overlapping region overlaps the character region, thedetermination module 250 determines that the content overlapping theoverlapping region is a character, or when the overlapping region doesnot overlap the character region, the determination module 250determines that the content overlapping the overlapping region is not acharacter.

When the determination module 250 determines that the contentoverlapping the overlapping region is not a character, the correctionmodule 251 does not correct the vertical region (step S705) and ends theset of steps. When the content is not a character, the content is likelya photograph, a pattern, etc., and such a content is likely bright (highluminance value). Noise lines are conspicuous when they are brighterthan the document and are inconspicuous when they are darker than thedocument, thus, when a noise line overlaps a content other thancharacters, the noise line may preferably be left as is withoutcorrection. Whereas, when a noise line overlaps a content such as ruledlines, elimination of the noise line may also eliminate ruled lines. Thecorrection module 251 does not correct a noise line when the noise lineoverlaps other contents than characters, thereby preventinginappropriately correcting a noise line and exacerbating the correctionimage.

When the determination module 250 determines that the contentoverlapping the overlapping region is a character, the correction module251 estimates the character overlapping the overlapping region based onthe context of the content (step S706). The context is words, sentences,a text, etc., constituted by a plurality of characters.

FIG. 24 is a schematic view depicting an example of a correction imagein which a noise line region overlaps a character.

In the correction image 2400 depicted in FIG. 24, a character “r” 2402overlaps a noise line region 2401. When character recognition processingis performed on this correction image 2400, the character 2402 isunlikely to be recognized correctly (for example, mistakenly recognizedas “1”), while characters 2403 “L,” “i,” “b,” “r,” “a,” “y” that do notoverlap the noise line region 2401 are correctly recognized. Thus, thecorrection module 251 estimates the character 2402 overlapping the noiseline region 2401 based on the characters 2403 that do not overlap thenoise line region 2401.

For example, the information processing apparatus 200 stores a contexttable recording a variety of contexts and image patterns of charactersin the second storage device 220 in advance. The correction module 251retrieves and refers to the context table in the second storage device220 and identifies a context where characters that do not overlap thenoise line region match characters included in each context from amongthe contexts stored in the context table. Note that the correctionmodule 251 identifies a context that includes characters that do notoverlap the noise line region and are lined up in sequence except forthe character that overlaps the noise line region. Then, the correctionmodule 251 estimates the character that overlaps the noise line regionfrom the identified context.

Next, the correction module 251 corrects the noise line region using theestimated characters (step S707), and ends the set of steps. Thecorrection module 251 identifies the character portion of charactersthat do not overlap the noise line region and the background portion inthe periphery of the characters, and calculates the average value of thecolor values of the identified character portion and the average valueof the color values of the background portion for each RGB color. Thecorrection module 251 retrieves an image pattern of the estimatedcharacter from the second storage device 220, and generates an image bydefining each color value of pixels corresponding to the image patternas the calculated average value of the color values of the characterportion and defining each color value of other pixels as the calculatedaverage value of the color values of the background portion. Then, thecorrection module 251 corrects the noise line region by replacing thecharacter portion overlapping the noise line region with the generatedimage.

If a noise line is corrected by linear interpolation etc., when thenoise line overlaps a character, the character portion may possibly beblurred, erased, or destroyed. The correction module 251 can accuratelycorrect a character by replacing the whole character portion thatoverlaps the noise line region with a preset image pattern.

Alternatively, the correction module 251 may estimate a character thatoverlaps a noise line using a discriminator that has learned beforehandto output character information when an image in which a character and anoise line overlap each other is input. This discriminator learns inadvance using a plurality of images in which a character and a noiseline overlap each other by deep learning etc., and is stored in thesecond storage device 220 in advance. The correction module 251 inputsan image including a character portion that overlaps a noise line regionto the discriminator and acquires character information output from thediscriminator to estimate the character that overlaps the noise line. Insuch a case, the correction module 251 can accurately estimate acharacter that overlaps a noise line and appropriately correct thecharacter portion that overlaps the noise line region.

Alternatively, the context table may not be stored in the second storagedevice 220, yet instead, stored in a server (not shown) that connectsand communicates with the information processing apparatus 200. In sucha case, the correction module 251 transmits characters that do notoverlap the noise line region to the server via a communication circuit(not shown), receives a context that matches the characters from theserver, and estimates the character overlapping the noise line regionfrom the received context. Likewise, the discriminator may not be storedin the second storage device 220, and instead, stored in a server (notshown) that connects and communicates with the information processingapparatus 200. In such a case, the correction module 251 transmits animage including the character portion that overlaps the noise lineregion to the server via a communication circuit (not shown) andreceives information of characters that are in the character portionfrom the server.

In this way, the correction module 251 changes the method of correctinga noise line region according to the determination result of thedetermination module 250. Thus, the correction module 251 canappropriately correct a noise line region for each target overlappingthe noise line region.

Note that, in the image processing system 1, the image reading apparatus100 may have a second dirt substance detection processing module 242 andexecute the second processing, instead of the information processingapparatus 200. In such a case, the image reading apparatus 100 executesthe second processing after generating the correction image at step S111of FIG. 11 and detects a dirt substance from the correction image.

Alternatively, in the image processing system 1, the informationprocessing apparatus 200 may have a first dirt substance detectionprocessing module 162 and execute the first processing and confirmationprocessing, instead of the image reading apparatus 100. In such a case,the image reading apparatus 100 transmits the white reference imageacquired at step S101 of FIG. 11 to the information processing apparatus200. When having received a white reference image from the image readingapparatus 100, the information processing apparatus 200 executes thefirst processing, detects a dirt substance from the white referenceimage, and generates the warning and provides the warning to a user viathe display device 201. The information processing apparatus 200 furtherexecutes the confirmation processing and receives a confirmationoperation by a user via the operation device 202.

Further, the second dirt substance detection processing module 242 maydetect a dirt substance from the document image instead of thecorrection image in the second processing. In such a case, at step S112of FIG. 11, the image reading apparatus 100 transmits the documentimage, instead of or in addition to the correction image, to theinformation processing apparatus 200 and the information processingapparatus 200 acquires the document image as an input image.

Further, in the same way as the second dirt substance detectionprocessing module 242, the first dirt substance detection processingmodule 162 may specify a priority range for preferentially detectingdirt in the white reference image using a position in the correctionimage where a dirt substance is detected as indicated in the secondresult. In such a case, the first dirt substance detection processingmodule 162 calculates dirt degrees of pixels that are spaced apart fromone another by a first distance in a horizontal direction, withoutcalculating dirt degrees of all pixels in the white reference image.Whereas, the first dirt substance detection processing module 162 sets arange, in the white reference image, that is within a predetermineddistance from a position corresponding to the position where a dirtsubstance is detected in the correction image as a priority range. Withregard to the pixels within the priority range, the first dirt substancedetection processing module 162 calculates dirt degrees of pixels thatare adjacent to one another or spaced apart from one another in ahorizontal direction by a second distance that is shorter than the firstdistance. In this way, the first dirt substance detection processingmodule 162 can reduce the load of dirt detection processing whileselectively scanning a region where dirt is highly likely to be present,which allows efficient detection of dirt.

Alternatively, the image processing system 1 may include a plurality ofinformation processing apparatuses 200, instead of one, which mayjointly operate to share each processing in the overall processing andsecond processing. In such a case, the plurality of informationprocessing apparatuses 200 may be distributed over a network so that theimage processing service can be provided in the form of cloud computing.

As detailed above, the image reading apparatus 100 generates the warningwhen a dirt degree at the imaging position is severe, or generates thewarning when a dirt degree at the imaging position is moderate (orminor) only when the document scan count exceeds a threshold, yet, doesnot generate the warning in other cases. Thus, the image readingapparatus 100 can generate the warning at more appropriate timing whenthe imaging position is dirty.

Further, the image processing system 1 is provided with a light source124 in the image reading apparatus 100 so that the leading end or rearend of a document conveyed onto the transparent member 127 forms ashadow on the white reference member 126, whereby the image readingapparatus 100 detects a shadow region from a correction image anddetects a dirt substance from the detected shadow region. Thus, theimage processing system 1 can detect both white dirt substance and blackdirt substance from a shadow region and can better detect a dirtsubstance from a correction image.

Further, the image processing system 1 detects a shadow region from aregion outside the document region in the correction image and detectsnoise pixels, the number of which connected with one another in theshadow region is equal to or more than a predetermined number, as anoise line. Thus, the image processing system 1 can detect both whitenoise line and black noise line from a shadow region and can moreaccurately detect a noise line from an image.

Further, in the image processing system 1, a dirt substance detectionresult is fed back to and used by each other between the firstprocessing for detecting a dirt substance from a white reference imagebefore generation of data for shading correction and the secondprocessing for detecting a dirt substance from the correction imageobtained by performing shading correction on a document image. Thus, theimage processing system 1 can better detect a dirt substance from animage.

FIG. 25 is a view depicting schematic components of an imaging unit 318according to another embodiment.

A first imaging unit 318 a and a second imaging unit 318 b depicted inFIG. 25 are used instead of the first imaging unit 118 a and the secondimaging unit 118 b in the image reading apparatus 100. In the firstimaging unit 318 a, a first light source 324 a is provided on thedownstream side of the first imaging sensor 125 a in a documentconveyance direction A3. In the second imaging unit 318 b, a secondlight source 324 b is provided on the upstream side of the secondimaging sensor 125 b in the document conveyance direction A3. Note thatthe first light source 324 a and the second light source 324 b may beprovided on the upstream side of the first imaging sensor 125 a.Alternatively, the first light source 324 a and the second light source324 b may be provided on the downstream side of the first imaging sensor125 a. The arrangement of each imaging sensor 125 and light source 324is indicated in the device information, and the information processingapparatus 200 can acquire the arrangement of each imaging sensor 125 andlight source 324 from the device information.

The image processing system according to this embodiment can alsoprovide the same effects as those described above.

FIG. 26 depicts schematic components of the imaging unit 418 and aconveyance mechanism of the upstream and downstream sides of the imagingunit 418 according to still another embodiment.

In this embodiment, an imaging unit 418, a first conveyance roller 415,a first driven roller 416, a second conveyance roller 420, and a seconddriven roller 421 are arranged upside down in a direction A4perpendicular to the document conveyance path in contrast to thearrangement state depicted in FIG. 4.

That is, the first imaging unit 418 a is arranged below the secondimaging unit 418 b. The first imaging unit 4I 8 a is provided with animaging unit guide 422. The second imaging unit 418 b is fixed to theupper housing 102 and the first imaging unit 418 a is supported by thelower housing 101 so that the first imaging unit 418 a can move in adirection perpendicular to the document conveyance path and is energizedin a direction toward the side of the second imaging unit 418 b by anenergizing spring 423. The first white reference member 426 a isprovided below the first transparent member 427 a, and the second lightsource 424 b and the second imaging sensor 425 b are provided on theopposite side of the first white reference member 426 a across the firsttransparent member 427 a and the second transparent member 4276.Likewise, the second white reference member 426 b is provided above thesecond transparent member 427 b, and the first light source 424 a andthe first imaging sensor 425 a are provided on the opposite side of thesecond white reference member 426 b across the first transparent member427 a and the second transparent member 427 b.

Further, the first driven roller 416 and the second driven roller 421are arranged below the first conveyance roller 415 and the secondconveyance roller 420 respectively. The first conveyance roller 415 andthe first driven roller 416 convey a document such that the document isconveyed along the second transparent member 427 b at the imagingpositions L1 and L2.

The image processing system according to this embodiment can alsoprovide the same effects as those described above.

FIG. 27 is a block diagram depicting schematic components of a firstprocessing circuit 180 according to another embodiment.

In place of the first CPU 160, the first processing circuit 180 performsthe overall processing, first processing, confirmation processing,threshold setting processing etc. The first processing circuit 180includes a first image acquiring circuit 181, a first dirt substancedetection processing circuit 182, a correction data generation circuit189, a correction image generation circuit 190 etc. The first dirtsubstance detection processing circuit 182 includes a first resultacquiring circuit 183, a dirt degree calculation circuit 184, anotifying circuit 185, a setting circuit 186, a threshold acquiringcircuit 187, an information acquiring circuit 188, etc.

The first image acquiring circuit 181 is an example of the first imageacquiring module and has the same function as the first image acquiringmodule 161. The first image acquiring circuit 181 acquires a whitereference image and a document image from the imaging unit 118, outputsthe acquired white reference image to the dirt degree calculationcircuit 184 and the correction data generation circuit 189 and outputsthe acquired document image to the correction image generation circuit190.

The first dirt substance detection processing circuit 182 is an exampleof the first dirt substance detection processing module and has the samefunction as the first dirt substance detection processing module 162.The first dirt substance detection processing circuit 182 performs thefirst processing for detecting a dirt substance from a white referenceimage.

The first result acquiring circuit 183 is an example of the first resultacquiring module and has the same function as the first result acquiringmodule 163. The first result acquiring circuit 183 acquires a secondresult from the information processing apparatus 200 via the firstinterface device 135, and outputs the second result to the notifyingcircuit 185, the setting circuit 186, and the correction data generationcircuit 189.

The dirt degree calculation circuit 184 is an example of the dirt degreecalculation module and has the same function as the dirt degreecalculation module 164. The dirt degree calculation circuit 184 acquiresa white reference image from the first image acquiring circuit 181 andeach threshold from the first storage device 140, calculates a dirtdegree at the imaging position from the white reference image, andoutputs the dirt degree to the notifying circuit 185.

The notifying circuit 185 is an example of the notifying module and hasthe same function as the notifying module 165. The notifying circuit 185acquires a dirt degree from the dirt degree calculation circuit 184, asecond result from the first result acquiring circuit 183, andopen/close information from the information acquiring circuit 188, andgenerates and provides the warning on the display operation device 106according to the dirt degree.

The setting circuit 186 is an example of the setting module and has thesame function as the setting module 166. The setting circuit 186acquires a binarization threshold from the threshold acquiring circuit187 and a second result from the first result acquiring circuit 183 andsets each threshold in the first storage device 140.

The threshold acquiring circuit 187 is an example of the thresholdacquiring module and has the same function as the threshold acquiringmodule 167. The threshold acquiring circuit 187 acquires a binarizationthreshold from the information processing apparatus 200 via the firstinterface device 135 and outputs the binarization threshold to thesetting circuit 186.

The information acquiring circuit 188 is an example of the informationacquiring module and has the same function as the information acquiringmodule 168. The information acquiring circuit 188 acquires an open/closesignal from the open/close sensor 114 and outputs the open/closeinformation to the notifying circuit 185.

The correction data generation circuit 189 is an example of thecorrection data generation module and has the same function as thecorrection data generation module 169. The correction data generationcircuit 189 acquires a white reference image from the first imageacquiring circuit 181 and a second result from the first resultacquiring circuit 183, generates data for shading correction from thewhite reference image, and outputs the data for shading correction tothe correction image generation circuit 190.

The correction image generation circuit 190 is an example of thecorrection image generation module and has the same function as thecorrection image generation module 170. The correction image generationcircuit 190 acquires a document image from the first image acquiringcircuit 181 and data for shading correction from the correction datageneration circuit 189, and generates a correction image by correctingthe document image using the data for shading correction. The correctionimage generation circuit 190 outputs the correction image to theinformation processing apparatus 200 via the first interface device 135.

The image processing system according to this embodiment can alsoprovide the same effects as those described above.

FIG. 28 is a block diagram depicting schematic components of a secondprocessing circuit 260 according to another embodiment.

In place of the second CPU 240, the second processing circuit 260preforms the overall processing, second processing, correctionprocessing etc. The second processing circuit 260 includes a secondimage acquiring circuit 261, a second dirt substance detectionprocessing circuit 262, a determination circuit 270, a correctioncircuit 271 etc. The second dirt substance detection processing circuit262 includes a second result acquiring circuit 263, a device informationacquiring circuit 264, an edge pixel extracting circuit 265, a documentregion detecting circuit 266, a shadow region detecting circuit 267, anoise pixel extracting circuit 268, a noise line detecting circuit 269etc.

The second image acquiring circuit 261 is an example of the second imageacquiring module and has the same function as the second image acquiringmodule 241. The second image acquiring circuit 261 acquires a correctionimage from the image reading apparatus 100 via the second interfacedevice 203, and outputs the acquired correction image to the edge pixelextracting circuit 265 and the correction circuit 271.

The second dirt substance detection processing circuit 262 is an exampleof the second dirt substance detection processing module and has thesame function as the second dirt substance detection processing module242. The second dirt substance detection processing circuit 262 performsthe second processing for detecting a dirt substance from a correctionimage.

The second result acquiring circuit 263 is an example of the secondresult acquiring module and has the same function as the second resultacquiring module 243. The second result acquiring circuit 263 acquiresthe first result from the image reading apparatus 100 via the secondinterface device 203 and the second result from the noise line detectingcircuit 269, and outputs the acquired first result and second result tothe noise pixel extracting circuit 268 and the noise line detectingcircuit 269.

The device information acquiring circuit 264 is an example of the deviceinformation acquiring module and has the same function as the deviceinformation acquiring module 244. The device information acquiringcircuit 264 acquires device information from the image reading apparatus100 via the second interface device 203 and outputs the acquired deviceinformation to the shadow region detecting circuit 267.

The edge pixel extracting circuit 265 is an example of the edge pixelextracting module and has the same function as the edge pixel extractingmodule 245. The edge pixel extracting circuit 265 acquires a correctionimage from the second image acquiring circuit 261, extracts first edgepixels from the correction image, and outputs the extracted first edgepixel information to the document region detecting circuit 266.

The document region detecting circuit 266 is an example of the documentregion detecting module and has the same function as the document regiondetecting module 246. The document region detecting circuit 266 acquiresthe first edge pixel information from the edge pixel extracting circuit265, detects a document region based on the first edge pixels, andoutputs the detected document region information to the shadow regiondetecting circuit 267.

The shadow region detecting circuit 267 is an example of the shadowregion detecting module and has the same function as the shadow regiondetecting module 247. The shadow region detecting circuit 267 acquiresdocument region information from the document region detecting circuit266, detects a shadow region from within a predetermined range outsidethe document region, and outputs the detected shadow region informationto the noise pixel extracting circuit 268.

The noise pixel extracting circuit 268 is an example of the noise pixelextracting module and has the same function as the noise pixelextracting module 248. The noise pixel extracting circuit 268 acquiresthe shadow region information from the shadow region detecting circuit267 and the first result and the second result from the second resultacquiring circuit 263, extracts noise pixels from the shadow region, andoutputs the extracted noise pixel information to the noise linedetecting circuit 269.

The noise line detecting circuit 269 is an example of the noise linedetecting module and has the same function as the noise line detectingmodule 249. The noise line detecting circuit 269 acquires the noisepixel information from the noise pixel extracting circuit 268 and thefirst result and the second result from the second result acquiringcircuit 263, detects a noise line based on the noise pixels, and outputsthe noise line region information to the determination circuit 270.

The determination circuit 270 is an example of the determination moduleand has the same function as the determination module 250. Thedetermination circuit 270 acquires the noise line region informationfrom the noise line detecting circuit 269, determines whether the noiseline region overlaps a content, and outputs the determination result tothe correction circuit 271.

The correction circuit 271 is an example of the correction module andhas the same function as the correction module 251. The correctioncircuit 271 acquires a correction image from the second image acquiringcircuit 261 and a determination result from the determination circuit270, corrects the correction image based on the determination result,stores the corrected correction image in the second storage device 220,and displays it on the display device 201.

The image processing system according to this embodiment can alsoprovide the same effects as those described above.

According to the image reading apparatus, the image processing system,and the dirt substance detection method, it is possible to easier betterdetect a dirt substance from an image of a document and a periphery ofthe document.

All examples and conditional language recited herein are intended forpedagogical purposes to aid the reader in understanding the inventionand the concepts contributed by the inventor to furthering the art, andare to be construed as being without limitation to such specificallyrecited examples and conditions, nor does the organization of suchexamples in the specification relate to a showing of the superiority andinferiority of the invention. Although the embodiment(s) of the presentinventions have been described in detail, it should be understood thatthe various changes, substitutions, and alterations could be made heretowithout departing from the spirit and scope of the invention.

What is claimed is:
 1. An image reading apparatus comprising: atransparent member; a white reference member provided either above orbelow the transparent member; an imaging device provided on an oppositeside of the white reference member across the transparent member; aconveyance member; a light source positioned on an opposite side of thewhite reference member across the transparent member, for irradiatinglight toward the white reference member; and a processor for detecting adirt substance from the input image, wherein the light source ispositioned such that a shadow of a leading end or rear end of a documentconveyed on the transparent member is formed on the white referencemember at an imaging position of the imaging device, and the processorcauses the conveyance member to convey the document between thetransparent member and the imaging device, causes the imaging device togenerate an input image of the document and a periphery of the conveyeddocument irradiated by the light source at the imaging position, detectsa shadow region formed by the leading end or rear end of the conveyeddocument irradiated by the light source, from the input image, detects adirt substance from within the detected shadow region, and outputsinformation related to the detected dirt substance.
 2. The image readingapparatus according to claim 1, wherein the white reference member isspaced apart from the transparent member.
 3. The image reading apparatusaccording to claim 1, wherein the processor detects the dirt substancebased on a difference between a gradient value of the shadow region anda gradient value of the dirt substance.
 4. The image reading apparatusaccording to claim 1, wherein the image reading apparatus does not havea reflection member for reflecting light emitted from the light sourcetoward a side of the white reference member.
 5. The image readingapparatus according to claim 1, wherein the conveyance member conveysthe document such that the document is conveyed, at the imaging positionand along the transparent member.
 6. The image reading apparatusaccording to claim 5, wherein the conveyance member is a conveyanceroller pair including a first roller and a second roller opposed to thefirst roller and disposed on an opposite side of the white referencemember with respect to an upper surface of the transparent member fromthe first roller in a direction perpendicular to the transparent member,wherein a nip position of the conveyance roller pair is disposed on anopposite side of the white reference member with respect to the uppersurface of the transparent member in a direction perpendicular to thetransparent member, and wherein a rotation axis of the second roller isshifted from a rotation axis of the first roller toward a side of theimaging device.
 7. The image reading apparatus according to claim 1,wherein the light source is provided on an upstream side of the imagingdevice in the document conveyance direction.
 8. An image processingsystem comprising: an image reading apparatus including: a transparentmember; a white reference member provided either above or below thetransparent member; an imaging device provided on an opposite side ofthe white reference member across the transparent member; a conveyancemember; a light source positioned on an opposite side of the whitereference member across the transparent member, for irradiating lighttoward the white reference member; and a first processor; and aninformation processing apparatus including a second processor fordetecting a dirt substance from the input image, wherein the lightsource is positioned such that a shadow of a leading end or rear end ofa document conveyed on the transparent member is formed on the whitereference member at an imaging position of the imaging device, and thefirst processor causes the conveyance member to convey the documentbetween the transparent member and the imaging device, and causes theimaging device to generate an input image of the document and aperiphery of the conveyed document irradiated by the light source at theimaging position, the second processor detects a shadow region formed bythe leading end or rear end of the document conveyed by the conveyancemember and irradiated by the light source, from the input image detectsa dirt substance within the detected shadow region, and outputsinformation related to the detected dirt substance.
 9. A dirt substancedetection method for an image reading apparatus, the method comprising:causing a conveyance member to convey a document between a transparentmember and an imaging device provided on an opposite side of a whitereference member above or below the transparent member and across thetransparent member; causing the imaging device to generate an inputimage of the document and a periphery of the conveyed documentirradiated by a light source; irradiating light from the light sourcetoward the white reference member such that a shadow of a leading end orrear end of the conveyed document is formed on the white referencemember at the imaging position; detecting a shadow region formed by theleading end or rear end of the conveyed document irradiated by the lightsource, from the input image; detecting a dirt substance within thedetected shadow region; and outputting information related to thedetected dirt substance.